"Connecting....." in Bambu Studio

BTW: I also tried to use my smartphone as hotspot to prevent that my home network (or my provider) is the problem…

LAN only mode does not help, too.

Interesting enough: If I power down the printer, BambuStudio presents the “Can’t connect to printer” message. If it is powered up, the “Connecting…” is presented again…

How can I debug this - is there any description of the protocol how printer and BambuStudio are communicating that may help with wireshark?