We were facing one of the following problem:
[wpfmb type=’error’ theme=2]SERVICE CURRENTLY NOT AVAILABLE!
Error No. [/wpfmb]
This problem occurs because of Roundcube database structure has not updated properly.
There is a very simple command to resolve the issue:
1) Login to the server as root
2) Just run the following command on a cPanel server.
This command will update the round cube forcefully on the server and should now resolve the issue.