Unable to Configure VCenter for VM backup, showing error.

I have added VCenter in customer environment 1 year back. Recently they have reset/ changed the VCenter password for compliance issue. After that from client, i have updated the new password, But after that i was not able to take any VM backup.

If I click, add backup> select Vcenter> select cellmanager as client, then the system hung UP for a while (around 20 min) after that it shows error. I am not able to start the existing backup as the doing the same error after hanging 20 min.

Tried to delete client and add client (Vcenter) but no luck.

cell manager is in Linux server, DP version 10.03.