NetApp Filer - CIFS shares backup failure

Hi there. 
We have a NetApp A150 filer with ONTAP 9.15 C mode as storage.  I upgraded BE to version 24 in November and then we had a licensing problem and it was downgraded back to version 23. Everything was working fine before. As soon as I downgraded (fresh install and configuration), everything keeps failing. I managed to fix the Vcenter backup but the file share still fails, nothing has changed on the NetApp side.  Support is unhelpful, pointing out that version 9.15 has not been tested.  The error message is : 

Monday, January 6, 2025 12:51:18 PM - V-79-57344-3844 - The Backup Exec server was unable to connect to the Remote Agent on machine "Filer name". The Backup Exec server will use the local agent to try to complete the operation. WARNING: Backup Exec servers cannot completely protect remote Windows-based servers or workstations unless the Backup Exec Remote Agent is installed and running on each remote Windows-based server or workstation to be protected. Data loss can occur if the Remote Agent is not running while backing up remote Windows-based computers. Please refer to the documentation or online help for more information. Backup Exec server is running Backup Exec version 23.0.1250.0.

There is/was  no agent installed on filer ever. If anyone has experienced the same issue I would appreciate some suggestions. Thank you in advance