In-Place SSRS 2014 to 2016 Upgrade Failed. Cannot start new SSRS 2016 instance

We have a SQL server 2014 and SSRS 2014 instance set up on two different 2012 R2 servers. This has been our setup for years, and everything has worked fine. We did an in place upgrade of the SQL server from 2014 to 2016 with no issues, but when I tried an in place upgrade of SSRS 2014 to 2016, it completed the setup with errors. The error we initially recieved on setup is “Index was out of Range. Must be non-negative and less than the size of the collection. Parameter name: index”. Now we are unable to start the SSRS instance. These errors appear to be an authentication issue. When I try starting the instance, I receive the following errors: > “Starting report server “ReportServer$NVSLDS2T080SSRS on NVSLDS-2T080. > The Task Failed. > > “System.InvalidOperationException: Cannot start service > ReportServer$NVSLDS2T080SSRS on computer 'NVSLDS-2T080'. ---> > System.ComponentModel.Win32Exception: Access is denied --- End of > inner exception stack trace --- at > System.ServiceProcess.ServiceController.Start(String[] args) at > System.ServiceProcess.ServiceController.Start() at > ReportServicesConfigUI.Panels.ConfigurationPanelWithErrors.StartOrStopServiceTask(Boolean > start, String serviceName)” The Event Viewer is also saying: - Event ID 7000 “The SQL Server Reporting Services (NVSLDS2T080SSRS) service failed to start due to the following error: Access is denied.” - Event ID 64, “Certificate for local system with Thumbprint 89 91 b4 e0 3a 96 cf ea a2 75 8f aa b6 41 e4 e5 c2 d3 69 aa is about to expire or already expired.” - Event ID 16 “The access history in hive \??\C:\Windows\System32\SMI\Store\Machine\SCHEMA.DAT was cleared updating 0 keys and creating 0 modified pages.” I haven't found many clear articles on the issue. The closest I have gotten is an article about the KB 2677070 update, which I don't believe to be the issue. https://support.microsoft.com/en-us/help/2745448/you-cannot-start-sql-server-reporting-services-after-you-apply-the-upd An issue with ASP.net: https://support.microsoft.com/en-us/help/332215/fix-system-argumentoutofrangeexception-index-was-out-of-range-error-oc . Please advise.