Always On Availability Groups MSSQL2017 Standard Edition - backup error

Good afternoon. We have two MSSQL2017 Standard Edition servers installed with the latest updates. 

On this servers created Always On Availability Groups. Backup Exec agent installed to this servers.

The Availability Group is visible in the backupexec admin panel, the databases are also in it.

When starting a backup task, we see an error:

0xe000846b - Make sure the server is online and that the correct version of Agent for Windows is installed. Final error category: HEX resource errors For details about this error, go to V-79-57344-33899.

Backup- ***Undefined host***V-79-57344-33899 - Server backup failed. Make sure the server is online and that the correct version of Agent for Windows is installed.

The MSSQL and Backup Exec server are on the same network and all ports are open.

Bases on the same servers that are not included in the AG are backed up normally. What could be the reason ?

Sincerely.