Unspecified error on backup "one or more errors"

Support
4

System.TimeoutException: HTTP timeout 00:01:40 exceeded
…
at Duplicati.Library.Backend.MicrosoftGraphBackend
…
at Duplicati.Library.Main.Operation.Backup.BackendUploader

suggests your Remote volume size on Options screen 5 isn’t uploading before the default timeout.
Default size is 50 MB, but one can change it (sometimes for good reasons, sometimes by accident).

Choosing sizes in Duplicati

If you like the remote volume size you’re using, try increasing http-operation-timeout to a higher value.