Is User Account Control turned off on the VM? Is the account you're using for Credentials a local Admin of the VM? Also, Guest Processing isn't needed unless you have some "service" (Active Directory for example) running on the VM, or for DB backup. 

How could I turn off User Account Control on the VM? 

I use a Windows 11 test version without a product key.

The account I use in Veeam for that VM is a local user who is a member of the administrator group. Could that be a problem?

Guest processing is disabled for that backup job.

See below on how to disable uac

Also, can you provide a screenshot of the area where you're getting your error to better understand & assist you? 

Thanks 

I disabled user account control but the backup job still fails:

Do you need more information?

Thanks for sharing. I actually think I understand now. How are you trying to backup your Win11 VM? Veeam doesn't support Vbox....just VMware & Hyper-V platforms (& Cloud too).

How are you adding your VM? Veeam doesn't use credentials unless you have guest processing enabled in your job.

The only way you can back up a VBox VM with Veeam is to use the Veeam Agent for Windows, then backup up the VM locally or manage it via Backup & Replication

It is a Windows computer backup job (type Windows Agent Backup), job mode type server, managed by backup server.

Do I need to install the Veeam Windows Backup Agent manually on the VM?

I had guest processing active at the beginning to backup SQL server transaction logs but disabled it later.

Ok...now that makes sense. So, the error you're getting I believe is from your scan of the VM from the Protection Group. Whatever credential you're using in your Protection Group isn't working. 

I would try to install the Agent manually, then add your VM to a Protection Group, then try to back it up. 

Can you get to the admin$ or c$ share of the VM from the server with Veeam on.

Creds will usually be %computername%\%username% or \%username%

There is not shared folder or drive on the VM. Do I need to share the C drive? 

If you do net share from a terminal (Admin) window you should have a few default shares such as C$, IPC$ and ADMIN$

It’s shared automatically. Open File Explorer, and in Explorer ‘address bar’ type in:

\\name-of-vm-or-ip\c$ , then press ENTER . You should be prompted to enter credentials. You need to use the format domain\username if the VM is on a domain, then password; or, if it’s a local user account you want to use to connect to the VM, enter .\username (yes, the dot needs to be there), then password. If you connect successfully, you will see the folder structure of the VM display in Explorer. You then need to use the same credentials in your Protection Group you added the VM to in Veeam B&R.

@chris392 - I created a new win11test VM, albeit in vSphere...to test this process myself. When adding a VM to a Protection Group (no Agent previously installed, like yours), and when using a local admin account, I get this same error. So, I went to the VAW User Guide & looked at the adding credentials section here. It appears the username is not supposed to be in the format I shared, but rather in the the format hostname\username. I am now testing this to see if I can connect.

Ok @chris392 , I figured this issue out. The error you’re receiving doesn’t occur with Domain accounts. It occurs only with local accounts; even with local admin accounts. The problem occurs due to remote UAC restrictions. To mitigate the issue, do the following:

After you perform the above, go back to your Veeam server and test your credentials again, using the local account format I specified above (hostname\username). It should then be successful.

That took some doing. But it is working now. Thanks so much @coolsport00!

I still get some errors with the backup though. But that is something to take care of tomorrow.

Yep; glad to help out.

Shane beat me to it.  The workload need to be a member of the domain, or else it does not allow access using the agent until you add the registry key noted because the default shares aren’t created for access in workstation mode by default.

Have you found a solution to the problem? I have exactly the same problem and none of the methods described help. I'm trying to attach a HyperV Windows 2022 Standard host - a fresh system connected to the domain. I log in with a domain account that has local administrator rights.

Ok @chris392 , I figured this issue out. The error you’re receiving doesn’t occur with Domain accounts. It occurs only with local accounts; even with local admin accounts. The problem occurs due to remote UAC restrictions. To mitigate the issue, do the following:

 

After you perform the above, go back to your Veeam server and test your credentials again, using the local account format I specified above (hostname\username). It should then be successful.

Thanks for posting this! I added this reg key to the non-domain workstation I needed backed up with Veeam. After verifying several times I had the password correct, it was this setting that made me able to add this server into our agent backup.

Glad to hear it helped you @backoops !