Exta Free: No synchronisation and reading of sensor status after changing phone

Let me start by saying that I have had an "installation" based on this system for a long time now, including an EFC02 controller plugged into my router. I have a fixed IP so theoretically everything is running, or actually was running, correctly until I replaced my mobile camera with a newer model. After installing the application (I use the exta free application ver. 2.1, controller software version 2.3.1), I log into the EFC02, but only as if in one direction, i.e. I can switch on, switch off etc. It is not possible to read the status of the sensors. It is not possible to read the status of the sensors or the time functions which are stored on the controller, and when trying to synchronise, the application displays "synchronisation error". At first I blamed the router, which I also replaced in the meantime, but no port forwarding or DMZ and other settings had any effect. And I have the same on 2 Samsung phones , where I have uninstalled everything that could interfere with communication. Surprisingly, when I took the old phones out of the drawer and connected via the internet to the EFC02 everything worked without any problems. For testing I also installed Android on my laptop and after installing exta free it also connects to the EFC controller "both ways" via internet of course. Has anyone already solved such a problem ? I would be happy to hear any suggestions as I have run out of ideas.

Hmmm, just reheating .