Today I walked into a problem with Veeam Endpoint on a server. The backup didn’t work and I received the error displayed below. When I started the backup-job. 
Error: Cannot proceed with the job: existing backup meta file ‘Backup Job\Backup Job.vbm’ on repository ‘BackupStorage’ is not synchronized with the DB. To resolve this, run repository rescan
Job has been stopped with failures. Name: [Backup Job], JobId: [fce0ff07-244b-48c8-9ab5-8c7bcc22d068] Error: Cannot proceed with the job: existing backup meta file ‘Backup Job SERVER\Backup Job.vbm’ on repository ‘BackupStorage’ is not synchronized with the DB. To resolve this, run repository rescan.
This problem can occur when you use the Veeam backup storage location ( same is in the normal Veeam backup and replication program)
Go in the dashboard to configure backup.
Select Entire Computer (this is default selected) click on next
It might be possible you have selected before Veeam Backup & replication repository
Change the setting to Shared Folder and click on next
Enter the backup destination and the administrator credentials and the restore points of the backup. click on next
Select the time when you want to do the backup. And click on next
Control if the settings are correct and click on finish, you can select run the job when i click finish. To see if the backup will run.
This was a solution for me to fix this problem