@Fvalphen73 Google Gemini gave me the advise that worked. Updating firmware on both existing XE75 devices from the DECO app (which was indeed required) immediately solved the issue. New XE75 was...

I have an issue with adding one XE75 to an existing mesh network of 2 XE75 routers. The new router just doesn't get detected by the DECO app. It did connect once or twice but then it seemed it then...