Same issue! Still not able in FW 3.7 it always tries to establish a connection with no user and password. And that even fails to connect. I just see it in mqtt logging. Tried with IPhone, Android phones. Tested with different router. Did a factory reset nothing solved the issue. Even testen multiple MQTT broker.
How can I enable debugging to see what nuki does?
Maybe an issue with my ip range or how nuki checks it. 172.20.x.x