Are you able to provide more details and error messages you are seeing in your jobs?  Also check the logs as well to see what is causing the issue - logs are found at -

C:\ProgramData\Veeam\Backup\<Job Folder>

Logs show that it is unable to access the 

p07.02.2023 23:07:38] <44> Error        Failed to prepare VM for processing: Unable to perform installation
<07.02.2023 23:07:38] <44> Error        Cannot upload guest agent's files to the admin share  i\\servername\ADMIN$\VeeamVssSupport].
o07.02.2023 23:07:38] <44> Error        Failed to delete directory l&1]
07.02.2023 23:07:38] <44> Error        Cannot remove folder n\\sservername\ADMIN$\VeeamVssSupport].
m07.02.2023 23:07:38] <44> Error        Cannot delete file �\\sservername\ADMIN$\VeeamVssSupport\OracleVssSupport.dll].
e07.02.2023 23:07:38] <44> Error        Cannot reset the read-only flag. File path: r\\servername\ADMIN$\VeeamVssSupport\OracleVssSupport.dll].
r07.02.2023 23:07:38] <44> Error        Cannot get file attributes. File path: e\\servername\ADMIN$\VeeamVssSupport\OracleVssSupport.dll].
r07.02.2023 23:07:38] <44> Error        Win32 error:Access is denied.
W07.02.2023 23:07:38] <44> Error         Code: 5 (System.Exception)
 

Have opened a case with support since last week. Hoping to get another perspective on the issue.

To me looks like potentially a permission issue or possible firewall changes.  Some things to check but this may require Support to help further as this is not something we can give an exact answer to unless someone has had the same issue.  

That’s what I’m hoping for that somebody has encountered the issue before. 

Yes, currently working with support right now but still unable to find a resolution without rebooting.

Hopefully support can get you to an answer.   Best of luck.

You cannot access the admin shares (ADMIN$, etc.).

Please see this forum thread:

https://forums.veeam.com/vmware-vsphere-f24/cannot-connect-to-the-host-s-administrative-share-t20833.html

That’s what the log says, can’t access or access denied. But that is not the case, I’ve checked that the service account that we use can access the admin$, it just cannot delete the VeeamVssSupport folder thus unable to install a new one to perform app aware backup. The folder is locked from the looks of it by a system process. 

We’re troubleshooting the same issue too @spider32, Ill let you know if our case with Veeam produces a solution.

Had the Veeam ticket close. Unable to determine what caused the issue and reboot is the only fix for now. Not seeing the re-occurrence of the issue in our environment.  

Same here @spider32, no definitive cause located in our ticket either.  We had this issue happen on a subset of VMs maybe 8 or 10 weeks ago, but chalked it up to a fluke, I suspect it will come back.

Maybe you could try to use the persistent guest agent for those VMs? It needs to be installed on those VMs and enabled in the Guest Processing/Application-Aware processing options. The persistent agent stays on the VM and does not get removed afterwards. So this could be a workaround for your issue.

https://helpcenter.veeam.com/docs/backup/vsphere/persistent_agent_components.html?ver=120

I have tried this and always had an issue but guess I need to test it again with v12 now. 

I have encountered an issue recently when I upgraded to v12 and caused issue on our physical servers. The installer service for some reason showed incompatible with the VBR although support said that it should be downward compatible. I saw some of the error messages as showing unable to access admin share. Maybe, the next time this occurs, as a workaround, I will try to uninstall the installer service. Will keep you guys posted. Thanks.