Traffic isn’t likely to be UDP given you want confirmation of it being delivered/received, but TCP:55414-5 are the two ports that you want to check for traffic…
Are you using DNS or the IP address for the server that the clients connect to, and what does the [UrBackup] server say about the clients…?
Depending on which way they’re using, I’d check that it’s able to establish a connection using PING to check resolution and pathing issues, and then TELNET or similar to check if the client servers are able to open the ports…
Checking the TCP ports 55414 and 55415 only shows the connection to the computer I run the management UI (55414).
What’s puzzling is I have two Fedora Servers with the same UrBackup client version. However once I have checked the firewall config I noticed a difference between the two. Once I synced the firewall config the server was discovered by the UrBackup server and works now