Add the below key to the registry location “HKEY_LOCAL_MACHINE\SOFTWARE\Veeam\Veeam Backup and Replication\” on the Veeam server. After applying the key make sure no jobs are running and restart the Veeam backup service.
The default value is 1200 so attempt doubling that value when creating the key.
Default value: 1200 (in seconds)
Description: Found in job log as "VSSControl: KeepSnapshot started, ttl 1200 sec". Registry setting was added in v9 update 1. Prior to that, this timeout was hard-coded to 600 seconds. This registry key goes to the Veeam Server