Homematic Binding with CCU - Error: "Unknown XML-RPC tag: title"

I am trying to get the Homematic binding up and running, yet it looks like I cannot connect the Binding with the RaspyMatic (i.e. the bridge).

This is the settting:
Openhab 2.4.0, running and I can access the PaperUI (installed: ntp and OpenWeatherMap)
RaspyMatic running on another host with static IP - I can access via WebUI, so this seems ok

As requested here (https://www.openhab.org/addons/bindings/homematic/) I opened ports


on the firewall, I also opened port 4349 on UDP for CCU autodiscovery (although I cannot see any trafic on this port). I opened the same ports on RaspyMatic.

Now I tried to setup the Add-on Homematic within Openhab PaperUI - I think only the Gateway Address has to point to the host of RaspyMatic, yet I also tried to set the Callback Network Address to the IP of the Openhab-Host.

I get the above error:

Any ideas? Can you give me a hint where to start debugging, as the log files of openhab don’t really help me.

Thanks a lot for any thought,