Are you like me and starting to explore with VB365 v8? Almost immediately after release Veeam identified a bug that leads to jobs failing. This has now been patched in KB4656.
If you’d like to read more about the root issue fixed there’s a good thread on the forums now. https://forums.veeam.com/veeam-backup-for-microsoft-365-f47/errors-on-upgrading-repo-s-v8-0-2-159-t95311.html