Server does not connect to client on VPN subnet

Hi, I just installed UrBackup on my Raspberry Pi in my homenetwork and it seems to work great so far. Backing up the Raspberry itself works perfectly. But now I want to Backup a remote Debian Server. The Raspberry is connected to the Server via Wireguard.
The UrBackup Client is installed on the remote server and I can Ping the remote Server (e.g. from my Raspberry ( When I add the Remote Server in UrBackup webinterface, I enter as a discovery hint. Then the server appears on the status page in a seperate hints section. Sometimes Online says yes and sometimes no. But the server never gets added completely.
Does anyone have an idea what I am doing wrong?
Thanks in advance for your help!

I see you did not get a response on this. Did you find your answer somewhere else?
This is exactly what I was wanting to do.

  1. Check iperf between urbackup server and server you want to backup.
  2. Check wan related issues: if you use async connection (if upload speed significantly lower than download) then try to lower mtu (1500 by default) to 1472 for example on your firewall/router.
  3. Check lan related issues (tcp checksummin, offloading etc.) on network adapters all things that works perfectly on 1gbps and low latency maters when connections established via high latency channels.
  4. Check firewall security features: filtering settings, logs.