In Veeam Backup & Replication version 9 and earlier, a UNC path may not be associated with a credentials record. If there is no associated record, the share is accessed using the account specified for the Veeam Data Mover Service (VeeamTransportSvc.exe). Local System is used by default. Use the Services MMC console (services.msc) to determine the account currently in use.
Note: It is possible to change the service account from this MMC console, but keep in mind that this service also determines the account used by data mover processes (VeeamAgent.exe), which can have an impact on other job types that access files on the Veeam Backup server. When changing the service account, make sure no jobs or restores are running before restarting the service.