Hi Patrick, I had a similar issue trying to connect via MQTT to an SPC Gateway (alarm system interface). I couldn’t get this method working as the MQTT broker on the system I was trying to connect to is only compatible with MQTT v3.1 clients, and as far as I can tell, OH > 2.5.0.M5 uses a later version of MQTT. I am trying to get it working using web sockets instead.
Check what MQTT client version is supported by the broker on the Roomba.