My German is not fit for a Forum, so here goes in english. Had a missing TRV after FW update. I managed to get i working again. Heres how.
My router client list showed the TRV as constantly switching between its AP IP address and a DHCP address given on my local network. Thus constantly dropping connection. I reset the TRV to make it go into AP mode, connected to the TRV AP network with my PC, and then accessed 192.168.33.1 in my browser using HTTP://192.168.33.1 - IMPORTANT HTTPS:// does not work, and most browsers asume you are trying a secure connection. Make sure to delete the "S".
From there I was able to configure Wi-FI, enable cloud and MQTT and now it is working again.
KR Morten