Was there any other solution than setting everything up again? I would definitely like to avoid that, as I currently have over 450 (Custom)Tonies on the box… 
I seem to have the same problem with my ESP32 after flashing the box due to the changed IP of the TC…
The box is displayed as online in Fritzbox and TC, and the TC can also be accessed via its IP in the browser, but there are no entries in the log when starting the box and performing a freshness check. Only the persisting code word Eule/Owl 
https://forum.revvox.de/t/trying-to-add-a-new-wlan-error-code-eule-owl/2926/23?u=schattenhexe
Edit:
Problem solved.
Apparently, it was the certificates and their assignment on the box, despite the lack of information in the log. I patched the original version without Teddycloud onto the box again, updated it once, then patched the version for Teddycloud again and reinstalled the certificates—now it works as before.