To "pretend" that VEB has a fresh install, do this in registry, go to the registry
Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Veeam\Veeam Endpoint Backup.
Go to the registry key called "RecreateDatabase" and set its value to 1. It will purge all data from Veeam Endpoint database (it will look like a fresh install). Veeam service restart is needed or computer restart is needed. PS: A full backup will be taken after that
But of course I want to know whether the first test solves your problem. It actually might indicate something that we need to investigate