CUPS: "server-error-internal-error"

My printer has been working fine for a while but I went to use it yesterday and it wouldn't print from my LM system (LinuxMint 21.3). The printer is still found and works from my Android phone and from a Windows 11 system; they still print without issue. And I can remove it and add it again under Windows without error. I can ping the printer successfully from LM but cannot add the printer either through the Cinnamon Printers applet or via the CUPS Webpage (http://127.0.0.1:631/) . Not sure what changed. It looks like the issue is empty PPD file (noted in the errors, below) but I'm not clear who this would have changed since this is the same printer that has been working for a long time and just stopped working with no obvious changes. I could really use some guidance on what to look for -- maybe some logs, determine whether the CUPS engine was recently updated, etc. Here's what I did... First, I deleted the existing, non-working printer and attempted to add the printer again. In the past, when it has stopped working, just re-adding it has been successful. Not this time; it fails with the "server-error-internal-error". As I was planning to go forward at some point, anyway, I installed an image of LinuxMint 22 (Wilma) to a new partition and tried to add the printer there. But the exact same results: Everything seems to indicate the printer is still found successfully but I'm unable to add it. I've searched around for references to the error and other apparently related issues. This seemed promising Remedy for CUPS Server Error on Linux but neither it nor the other things I've found have helped. **ippfind** reports this: ipp://Canonaaf616.local:631/ipp/print So, I went to the CUPS webpage (Administration, Add Printer/Find New Printers) and it successfully finds the printer: But having attempted to add the printer using all of the listed "Printers" and "Models", none of them have worked. Using the "IPP Everywhere" model returns: Unable to create PPD: No IPP attributes. Using the "driverless" model returns: cups-driverd failed to get PPD file - see error_log for details. Checking /var/log/cups/error_log, I see several messages like below for various languages: [cups-driverd] Bad driver information file \"/usr/share/ppd/openprinting/Utax/Global/English/... Followed by these: E [24/Sep/2024:12:07:17 -0600] Canon_MF741C_743C_: PPD creation failed: No IPP attributes. E [24/Sep/2024:12:07:17 -0600] [Client 572] Returning IPP server-error-device-error for CUPS-Add-Modify-Printer (ipp://localhost/printers/Canon_MF741C_743C_) from localhost. E [24/Sep/2024:12:08:06 -0600] [CGI] Unable to create PPD file: Could not poll sufficient capability info from the printer (ipps://Canon%20MF741C%2F743C%20(aa%3Af6%3A16)%20(aa%3Af6%3A16)%20(aa%3Af6%3A%20%20(2a%3A17%3A0e)%20(7)._ipps._tcp.local/, ipps: //Canonaaf616.local:10443/ipp/print) via IPP! E [24/Sep/2024:12:08:06 -0600] copy_model: empty PPD file E [24/Sep/2024:12:08:06 -0600] [Client 597] Returning IPP server-error-internal-error for CUPS-Add-Modify-Printer (ipp://localhost/printers/Canon_MF741C_743C_) from localhost. E [24/Sep/2024:12:08:21 -0600] [CGI] Unable to create PPD file: Could not poll sufficient capability info from the printer (ipps://Canon%20MF741C%2F743C%20(aa%3Af6%3A16)%20(aa%3Af6%3A16)%20(aa%3Af6%3A%20%20(2a%3A17%3A0e)%20(7)._ipps._tcp.local/, ipps: //Canonaaf616.local:10443/ipp/print) via IPP! E [24/Sep/2024:12:08:21 -0600] copy_model: empty PPD file E [24/Sep/2024:12:08:21 -0600] [Client 625] Returning IPP server-error-internal-error for CUPS-Add-Modify-Printer (ipp://localhost/printers/Canon_MF741C_743C_) from localhost. **avahi-browse -rt _ipp._tcp** returns: + wlp5s0 IPv6 Canon MF741C/743C (aa:f6:16) (aa:f6:16) (aa:f6: (2a:17:0e) (7) Internet Printer local + wlp5s0 IPv4 Canon MF741C/743C (aa:f6:16) (aa:f6:16) (aa:f6: (2a:17:0e) (7) Internet Printer local = wlp5s0 IPv6 Canon MF741C/743C (aa:f6:16) (aa:f6:16) (aa:f6: (2a:17:0e) (7) Internet Printer local hostname = [Canonaaf616.local] address = [192.168.4.31] port = txt = ["mopria-certified=1.3" "print_wfds=T" "rfo=ipp/faxout" "kind=document,envelope,postcard" "URF=ADOBERGB24,CP255,DM1,PQ4,RS300,SRGB24,W8-16,FN3,IS1-4,OB10-40,V1.4" "Fax=T" "Scan=T" "TLS=1.2" "usb_CMD=LIPSLX,CPCA" "UUID=6d4ff0ce-6b11-11d8-8020-349f7baaf616" "PaperMax=legal-A4" "Punch=0" "Staple=F" "Sort=F" "Collate=F" "Bind=F" "PaperCustom=T" "Duplex=T" "Copies=T" "Color=T" "TBCP=F" "Binary=F" "Transparent=F" "usb_MDL=MF741C/743C" "usb_MFG=Canon" "adminurl=http://Canonaaf616.local:80/airprint.html " "pdl=application/octet-stream,image/urf,image/pwg-raster,image/jpeg,application/pdf" "product=(CNMF741C/743C)" "ty=Canon MF741C/743C" "priority=10" "qtotal=1" "note=" "rp=ipp/print" "txtvers=1"] = wlp5s0 IPv4 Canon MF741C/743C (aa:f6:16) (aa:f6:16) (aa:f6: (2a:17:0e) (7) Internet Printer local hostname = [Canonaaf616.local] address = [192.168.4.31] port = txt = ["mopria-certified=1.3" "print_wfds=T" "rfo=ipp/faxout" "kind=document,envelope,postcard" "URF=ADOBERGB24,CP255,DM1,PQ4,RS300,SRGB24,W8-16,FN3,IS1-4,OB10-40,V1.4" "Fax=T" "Scan=T" "TLS=1.2" "usb_CMD=LIPSLX,CPCA" "UUID=6d4ff0ce-6b11-11d8-8020-349f7baaf616" "PaperMax=legal-A4" "Punch=0" "Staple=F" "Sort=F" "Collate=F" "Bind=F" "PaperCustom=T" "Duplex=T" "Copies=T" "Color=T" "TBCP=F" "Binary=F" "Transparent=F" "usb_MDL=MF741C/743C" "usb_MFG=Canon" "adminurl=http://Canonaaf616.local:80/airprint.html " "pdl=application/octet-stream,image/urf,image/pwg-raster,image/jpeg,application/pdf" "product=(CNMF741C/743C)" "ty=Canon MF741C/743C" "priority=10" "qtotal=1" "note=" "rp=ipp/print" "txtvers=1"] **avahi-browse -rt _uscan._tcp** returns: + wlp5s0 IPv4 Canon MF741C/743C (aa:f6:16) (aa:f6:16) (aa:f6: (2a:17:0e) (7) _uscan._tcp local = wlp5s0 IPv4 Canon MF741C/743C (aa:f6:16) (aa:f6:16) (aa:f6: (2a:17:0e) (7) _uscan._tcp local hostname = [Canonaaf616.local] address = [192.168.4.31] port = txt = ["usb_MFG=Canon" "mopria-certified-scan=1.2" "duplex=T" "is=platen,adf" "UUID=6d4ff0ce-6b11-11d8-8020-349f7baaf616" "cs=color,grayscale" "pdl=application/octet-stream,application/pdf,image/jpeg" "representation=" "adminurl=http://Canonaaf616.local:80/airprint.html " "rs=eSCL" "vers=2.63" "note=" "ty=Canon MF741C/743C" "txtvers=1"] **UPDATE** This appears to be some kind of change related to networking but nothing has changed on the network. - My "Home" firewall is disabled. - My router still shows the printer as connected. - I can ping the printer IP from any of the computers. - The LinuxMint "Find Network Printer" option finds the computer on the network. - The CUPS webpage can find the printer. - avahi-browse can find the printer. But all attempts fail to either: 1) add the printer on a Linux system, or 2) print to it from a Linux system that still has that printer added from before the issue. I tried creating the queue manually with lpadmin -p TEST -v ipp:///ipp/print -m everywhere -E but it returned lpadmin: Unable to create PPD: No IPP attributes. I found this article CUPS: “Unable to Copy PPD file" which seemed applicable. I checked my /etc/nswitch.conf and the contents are: # /etc/nsswitch.conf # # Example configuration of GNU Name Service Switch functionality. # If you have the glibc-doc-reference' and info' packages installed, try: # `info libc "Name Service Switch"' for information about this file. passwd: files systemd group: files systemd shadow: files systemd gshadow: files systemd hosts: files mdns4_minimal [NOTFOUND=return] dns myhostname networks: files protocols: db files services: db files ethers: db files rpc: db files netgroup: nis The hosts line looks correct, I think? I had no /etc/msdn.allow file so added one with the contents: .local. .local But no improvement; still cannot print or add the printer. **UPDATE** Apparently this is a bug in CUPS: Can't add Canon ipp printer after cups version 2.4.6