Logon account that was provided does not have the appropriate privileges to back up the SQL database

I checked and rechecked all my logon accounts. Same problems even with using the SA account.

Then I decided to remove and create the logons again in Backup Exec, and I created a new backup job in Backup Exec for that MSSQL server. Then in the selection list for the job I selected and only selected the MS Sql server and used the sa account. The backup worked, and most of the errors were gone except for these errors :

Backup- DICOMSERVER\MSSQLSERVER
Database \model was not found, or could not be accessed.

The backup options or selections for this job have changed since the last time it ran.

Backup- DICOMSERVER\MSSQLSERVER
V-79-57344-5891 - The object was not found, or could not be accessed (MS SQL backup). The item DICOMSERVER\MSSQLSERVER\model in use - skipped.

I then added the rest of the partitions/folders to the selection list in the backup job. Ran it again, and seems everything is fine still except for the database "model".