Cannot take image backup from windows server 2012

I configured a group for servers and allow image backup for this group but there is no image backup taken in the allowed times and when I press full image backup for any server the program give no response and do nothing despite of taking files backup normally on the same servers.
I tried to remove the client from these servers and install it again but the same problem exists.

Not much technical details here to help with.

Have you reviewed how LAN connections are made?
How Internet connections are made?
Checked firewalls?
Port Forwarding if appropriate?

There are no internet connection for the urbackup program.
The Backup server and all it’s clients in the same network.
The backup server and targeted servers in the same rack and connected to the same switch.
so I think it’s not a network problem.

Verify firewall status for this:
https://www.urbackup.org/administration_manual.html#x1-9000010.3

Urbackup server firewall is turned off and no need for firewall of gateway to configure because of urbackup server and all clients on the same network
also all file backups on all clients running normally but image backup not able to start on all clients knowing that I disabled image backup on all groups except group which named servers.