Why won't client show up on server?

Installed latest URBackup on nine clients and eight of them show up on the server(GUI) but the ninth one will not. All do an image backup but the ninth will not. Tried the ‘Add Client’ and shows up as online. Did a ping of the machine and was good. Uninstalled / Reinstalled but the same results. Now the client was working at one time but had to remove it for some reason and when I reinstalled, this problem showed up. I did restart after the uninstall. All are on the same network. I have another incident in this forum with the same issue but couldn’t really get an answer so I am trying again. The program seems to be good and would hate to replace it becuz of one client not working and it might be something simple.
Thank you

Check network, firewall settings, TCP ports 55415 from client to server.

Check if the client is configured as LAN or internet, if internet check DNS: nslookup, ping etc.