Error: Azure Backup fails Everyday and cannot decipher error message:

Open a command prompt and type... "vssadmin list writers"

You are looking for each writer to be - State: [1] Stable

You will typically see State 5, 7, or 11 on writers with issues.

Anything other than a 1 on certain writers will block the process. Server reboots do not usually fix the issue but sometimes can.

The easiest way is to restart the particular service connected to that writer. There are lists out on the web showing which service is tied to which writer.

One that is hard to find is if NTDS is in an errored state. Restart COM services for that one.

Keep checking until you get all in a stable state, (or as many as possible) and then run your backup.

Hope that helps.