SQL Server Agent not starting after in-place upgrade of SQL Server from 2012 to 2019

I have done an in-place upgrade of SQL Server from SQL Server 2012 Standard Edition (64-bit) SP4 to >Microsoft SQL Server 2019 (RTM) - 15.0.2000.5 (X64) Sep 24 2019 13:48:23 Copyright (C) 2019 Microsoft Corporation Standard Edition (64-bit) on Windows Server 2019 Datacenter 10.0 (Build 17763: ) (Hypervisor). After upgrading, the SQL Server Agent is in a stopped state. I have tried using the *Local System* account but still no luck. Error in Windows event logs is: > SQLServerAgent could not be started (reason: SQLServerAgent cannot start because the msdb database is read-only). I have checked and confirm that the *msdb* database is not in read only state. Can someone help me to resolve this issue. I am connected to the correct instance. I have applied the command:

ALTER DATABASE [msdb] SET READ_WRITE WITH NO_WAIT;

There was no error. The drive that stores *msdb* has not run out of space. No space issue as such. The SQL Server service account has access to the drive for those files. I do have backups of *msdb* from before the upgrade. ### Logs

-none
2023-04-05 15:22:13.640	Server	Microsoft SQL Server 2019 (RTM) - 15.0.2000.5 (X64)    Sep 24 2019 13:48:23    Copyright (C) 2019 Microsoft Corporation   Standard Edition (64-bit) on Windows Server 2019 Datacenter 10.0  (Build 17763: ) (Hypervisor)  
2023-04-05 15:22:13.650	Server	UTC adjustment: 1:00
2023-04-05 15:22:13.710	Server	(c) Microsoft Corporation.
2023-04-05 15:22:13.710	Server	All rights reserved.
2023-04-05 15:22:13.760	Server	Server process ID is 5180.
2023-04-05 15:22:13.760	Server	System Manufacturer: 'VMware, Inc.', System Model: 'VMware Virtual Platform'.
2023-04-05 15:22:13.760	Server	Authentication mode is MIXED.
2023-04-05 15:22:13.830	Server	Logging SQL Server messages in file 'C:\Program Files\Microsoft SQL Server\MSSQL11.MSSQLSERVER\MSSQL\Log\ERRORLOG'.
2023-04-05 15:22:13.840	Server	The service account is 'BICESTER\service_vrsunsql-01'. This is an informational message; no user action is required.
2023-04-05 15:22:13.870	Server	Registry startup parameters:     -d I:\DATA\master.mdf    -e C:\Program Files\Microsoft SQL Server\MSSQL11.MSSQLSERVER\MSSQL\Log\ERRORLOG    -l L:\LOGS\mastlog.ldf    -T 1118    -T 902
2023-04-05 15:22:13.870	Server	Command Line Startup Parameters:    -s "MSSQLSERVER"
2023-04-05 15:22:13.870	Server	Trace flag 1118 is discontinued. Use the options provided with ALTER DATABASE.
2023-04-05 15:22:14.430	Server	SQL Server detected 2 sockets with 2 cores per socket and 2 logical processors per socket, 4 total logical processors; using 4 logical processors based on SQL Server licensing. This is an informational message; no user action is required.
2023-04-05 15:22:14.430	Server	SQL Server is starting at normal priority base (=7). This is an informational message only. No user action is required.
2023-04-05 15:22:14.440	Server	Detected 24575 MB of RAM. This is an informational message; no user action is required.
2023-04-05 15:22:14.500	Server	Using conventional memory in the memory manager.
2023-04-05 15:22:14.550	Server	Page exclusion bitmap is enabled.
2023-04-05 15:22:14.980	Server	Buffer Pool: Allocating 4194304 bytes for 2785280 hashPages.
2023-04-05 15:22:15.800	Server	Default collation: Latin1_General_CI_AS (us_english 1033)
2023-04-05 15:22:18.770	Server	Buffer pool extension is already disabled. No action is necessary.
2023-04-05 15:22:20.090	Server	Query Store settings initialized with enabled = 1, 
2023-04-05 15:22:20.170	Server	The maximum number of dedicated administrator connections for this instance is '1'
2023-04-05 15:22:20.170	Server	This instance of SQL Server last reported using a process ID of 12452 at 05/04/2023 15:21:40 (local) 05/04/2023 14:21:40 (UTC). This is an informational message only; no user action is required.
2023-04-05 15:22:20.190	Server	Node configuration: node 0: CPU mask: 0x000000000000000f:0 Active CPU mask: 0x000000000000000f:0. This message provides a description of the NUMA configuration for this computer. This is an informational message only. No user action is required.
2023-04-05 15:22:20.250	Server	Using dynamic lock allocation.  Initial allocation of 2500 Lock blocks and 5000 Lock Owner blocks per node.  This is an informational message only.  No user action is required.
2023-04-05 15:22:20.320	Server	In-Memory OLTP initialized on lowend machine.
2023-04-05 15:22:20.480	Server	[INFO] Created Extended Events session 'hkenginexesession'  
2023-04-05 15:22:20.490	Server	Database Instant File Initialization: enabled. For security and performance considerations see the topic 'Database Instant File Initialization' in SQL Server Books Online. This is an informational message only. No user action is required.
2023-04-05 15:22:20.510	Server	Total Log Writer threads: 2. This is an informational message; no user action is required.
2023-04-05 15:22:20.640	Server	CLR version v4.0.30319 loaded.
2023-04-05 15:22:20.650	Server	clwb is selected for pmem flush operation.
2023-04-05 15:22:21.170	spid10s	Starting up database 'master'.
2023-04-05 15:22:21.200	Server	Common language runtime (CLR) functionality initialized using CLR version v4.0.30319 from C:\Windows\Microsoft.NET\Framework64\v4.0.30319\.
2023-04-05 15:22:21.470	Server	Software Usage Metrics is enabled.
2023-04-05 15:22:22.030	spid10s	SQL Server Audit is starting the audits. This is an informational message. No user action is required.
2023-04-05 15:22:22.100	spid10s	SQL Server Audit has started the audits. This is an informational message. No user action is required.
2023-04-05 15:22:22.500	spid10s	SQL Trace ID 1 was started by login "sa".
2023-04-05 15:22:22.540	spid10s	Server name is 'VRSUNSQL-01'. This is an informational message only. No user action is required.
2023-04-05 15:22:22.590	spid34s	The certificate [Cert Hash(sha1) "793CBB1F5F4CF0626C1920BEEA6E8D24E96E2C36"] was successfully loaded for encryption.
2023-04-05 15:22:22.600	spid34s	Server is listening on [ 'any'  1433].
2023-04-05 15:22:22.610	spid34s	Server is listening on [ 'any'  1433].
2023-04-05 15:22:22.630	spid34s	Server local connection provider is ready to accept connection on [ \\.\pipe\SQLLocal\MSSQLSERVER ].
2023-04-05 15:22:22.650	spid34s	Server named pipe provider is ready to accept connection on [ \\.\pipe\sql\query ].
2023-04-05 15:22:22.680	spid11s	Starting up database 'mssqlsystemresource'.
2023-04-05 15:22:22.690	Logon	Error: 17187, Severity: 16, State: 1.
2023-04-05 15:22:22.690	Logon	SQL Server is not ready to accept new client connections. Wait a few minutes before trying again. If you have access to the error log, look for the informational message that indicates that SQL Server is ready before trying to connect again.  [CLIENT: fe80::b425:769:1663:c836%10]
2023-04-05 15:22:22.700	spid36s	Starting up database 'msdb'.
2023-04-05 15:22:22.700	spid42s	Always On: The availability replica manager is starting. This is an informational message only. No user action is required.
2023-04-05 15:22:22.720	spid42s	Always On: The availability replica manager is waiting for the instance of SQL Server to allow client connections. This is an informational message only. No user action is required.
2023-04-05 15:22:22.720	Server	Server is listening on [ ::1  1434].
2023-04-05 15:22:22.720	spid38s	Starting up database 'SUNDB'.
2023-04-05 15:22:22.730	Server	Server is listening on [ 127.0.0.1  1434].
2023-04-05 15:22:22.740	spid39s	Starting up database 'SunSystemsSecurity'.
2023-04-05 15:22:22.750	Server	Dedicated admin connection support was established for listening locally on port 1434.
2023-04-05 15:22:22.760	spid40s	Starting up database 'QA10'.
2023-04-05 15:22:22.780	spid41s	Starting up database 'SapphirePowerTools'.
2023-04-05 15:22:22.800	spid34s	SQL Server is now ready for client connections. This is an informational message; no user action is required.
2023-04-05 15:22:22.820	Server	SQL Server is attempting to register a Service Principal Name (SPN) for the SQL Server service. Kerberos authentication will not be possible until a SPN is registered for the SQL Server service. This is an informational message. No user action is required.
2023-04-05 15:22:22.850	spid11s	The resource database build version is 15.00.2000. This is an informational message only. No user action is required.
2023-04-05 15:22:23.150	Server	The SQL Server Network Interface library could not register the Service Principal Name (SPN) [ MSSQLSvc/VRSUNSQL-01.valueretail.com ] for the SQL Server service. Windows return code: 0x21c7, state: 15. Failure to register a SPN might cause integrated authentication to use NTLM instead of Kerberos. This is an informational message. Further action is only required if Kerberos authentication is required by authentication policies and if the SPN has not been manually registered.
2023-04-05 15:22:23.150	Server	The SQL Server Network Interface library could not register the Service Principal Name (SPN) [ MSSQLSvc/VRSUNSQL-01.valueretail.com:1433 ] for the SQL Server service. Windows return code: 0x21c7, state: 15. Failure to register a SPN might cause integrated authentication to use NTLM instead of Kerberos. This is an informational message. Further action is only required if Kerberos authentication is required by authentication policies and if the SPN has not been manually registered.
2023-04-05 15:22:24.190	spid11s	Starting up database 'model'.
2023-04-05 15:22:25.290	spid38s	Parallel redo is started for database 'SUNDB' with worker pool size .
2023-04-05 15:22:25.300	spid40s	Parallel redo is started for database 'QA10' with worker pool size .
2023-04-05 15:22:25.350	spid39s	Parallel redo is started for database 'SunSystemsSecurity' with worker pool size .
2023-04-05 15:22:25.360	spid41s	Parallel redo is started for database 'SapphirePowerTools' with worker pool size .
2023-04-05 15:22:25.390	spid40s	Parallel redo is shutdown for database 'QA10' with worker pool size .
2023-04-05 15:22:25.440	spid38s	Parallel redo is shutdown for database 'SUNDB' with worker pool size .
2023-04-05 15:22:25.470	spid39s	Parallel redo is shutdown for database 'SunSystemsSecurity' with worker pool size .
2023-04-05 15:22:25.480	spid41s	Parallel redo is shutdown for database 'SapphirePowerTools' with worker pool size .
2023-04-05 15:22:25.560	spid11s	Clearing tempdb database.
2023-04-05 15:22:25.630	spid41s	CHECKDB for database 'SapphirePowerTools' finished without errors on 2023-04-02 00:09:22.080 (local time). This is an informational message only; no user action is required.
2023-04-05 15:22:25.650	spid39s	CHECKDB for database 'SunSystemsSecurity' finished without errors on 2023-04-02 00:09:18.850 (local time). This is an informational message only; no user action is required.
2023-04-05 15:22:25.740	spid38s	CHECKDB for database 'SUNDB' finished without errors on 2023-04-02 00:00:01.610 (local time). This is an informational message only; no user action is required.
2023-04-05 15:22:25.760	spid40s	CHECKDB for database 'QA10' finished without errors on 2023-04-02 00:09:21.510 (local time). This is an informational message only; no user action is required.
2023-04-05 15:22:25.770	spid36s	CHECKDB for database 'msdb' finished without errors on 2023-04-05 15:07:59.290 (local time). This is an informational message only; no user action is required.
2023-04-05 15:22:26.000	spid52	Configuration option 'Agent XPs' changed from 0 to 1. Run the RECONFIGURE statement to install.
2023-04-05 15:22:26.270	spid11s	Starting up database 'tempdb'.
2023-04-05 15:22:26.480	spid11s	The tempdb database has 1 data file(s).
2023-04-05 15:22:26.510	spid36s	The Service Broker endpoint is in disabled or stopped state.
2023-04-05 15:22:26.510	spid36s	Server is listening on [ 'any'  5022].
2023-04-05 15:22:26.510	spid36s	Server is listening on [ 'any'  5022].
2023-04-05 15:22:26.510	spid36s	The Database Mirroring endpoint is now listening for connections.
2023-04-05 15:22:26.710	spid36s	Service Broker manager has started.
2023-04-05 15:22:26.710	spid10s	Recovery is complete. This is an informational message only. No user action is required.
2023-04-05 15:22:26.910	spid52	Attempting to load library 'xpsqlbot.dll' into memory. This is an informational message only. No user action is required.
2023-04-05 15:22:26.970	spid52	Using 'xpsqlbot.dll' version '2019.150.2000' to execute extended stored procedure 'xp_qv'. This is an informational message only; no user action is required.
2023-04-05 15:22:27.150	spid52	Configuration option 'Agent XPs' changed from 1 to 0. Run the RECONFIGURE statement to install.
2023-04-05 15:23:35.040	spid56	Configuration option 'Agent XPs' changed from 0 to 1. Run the RECONFIGURE statement to install.
2023-04-05 15:23:35.070	spid56	Configuration option 'Agent XPs' changed from 1 to 0. Run the RECONFIGURE statement to install.
2023-04-05 15:27:13.920	Logon	Error: 18456, Severity: 14, State: 5.
2023-04-05 15:27:13.920	Logon	Login failed for user 'BICESTER\VRSUNSQL-01$'. Reason: Could not find a login matching the name provided. [CLIENT: ]
2023-04-05 15:28:03.600	spid60	Configuration option 'Agent XPs' changed from 0 to 1. Run the RECONFIGURE statement to install.
2023-04-05 15:28:03.640	spid60	Configuration option 'Agent XPs' changed from 1 to 0. Run the RECONFIGURE statement to install.
2023-04-05 15:29:26.920	spid51	Configuration option 'Agent XPs' changed from 0 to 1. Run the RECONFIGURE statement to install.
2023-04-05 15:29:26.960	spid51	Configuration option 'Agent XPs' changed from 1 to 0. Run the RECONFIGURE statement to install.
2023-04-05 15:29:30.880	spid51	Configuration option 'Agent XPs' changed from 0 to 1. Run the RECONFIGURE statement to install.
2023-04-05 15:29:30.910	spid51	Configuration option 'Agent XPs' changed from 1 to 0. Run the RECONFIGURE statement to install.
2023-04-05 15:32:14.500	Logon	Error: 18456, Severity: 14, State: 5.
2023-04-05 15:32:14.500	Logon	Login failed for user 'BICESTER\VRSUNSQL-01$'. Reason: Could not find a login matching the name provided. [CLIENT: ]