Avamar Manual backup/ODB is failing.

Manual backups are failing with timeout, however scheduled backups are working fine.

When we try manual backup, server is reaching the client - however client is not responding.

respective ports(28002) are listening, I have restarted the avagent service as well.

Customer is not agreeing to re-integrate the client - as they are scared that - it can't be integrated again.

Also from GUI - tried to invite the client - its failed to connect.

Question is  - why only manual backup is failing. any clues?