Ha, of course it works after you ask for help :D
Not completely sure if it had something to do with it, but I enabled "Accept new Hardware Devices" for a moment and after adding the Thermosmart hardware again all devices are visible.
Perhaps something to check if others are having the same problem ...

Hi, I'm trying to control my Thermosmart, but the only thing that's happening is a log entry with "Status: Thermosmart: Login successfull!..."
No new devices, setpoints, temperatures...

The added Thermosmart hardware says "Version: undefined", if that's of any help. But apart from the log entries ...