The starting point of the total failure was the insufficient installation of Fibaro FGBS222, where none of the connected DS18B20 temperature sensors were registered in the device table. Changes of the configurations do not seem to be taken over by the device. To solve the problem I have activated polling on a trial basis. Since then Domoticz is no longer accessible via web interface. Probably the ZWave network is overloaded with polling tasks.

As Z-Wave controller I use the USB stick ZMEEUZB1, about 40 Z-Wave devices are in operation, some for years. Now I have no access anymore! Stupidly I did not create any current backups the last months.

Fortunately I still have access to the Raspberry via Putty. Unfortunately I have only limited knowledge of Linux. I think that in a configuration file of the ZWave stick an entry has to be set back to "Disable Polling". To do this I would also need to get to the configuration file - but how? Would this be the right way? Are there alternatives or I have not yet understood the problem properly?
I will try to get new access to the web interface without plugged ZWave stick in order to make an inital backup. But this will not solve the problem...
I am grateful for any hint!