Thanks for your assistance, I am new at this.
Thought Shelly had MQTT built in the device, guess my settings are incorrect? I did not install external MQTT Broker.
It looks like the driver for Shelly Motion connects to the MQTT broker directly, so I assume it is even simpler to set up because an additional Hubitat MQTT app is not required.
Have no raspberry at hand at the moment but will try this on my QNAP or Synology NAS, they seem to have MQTT brokers you can install. Thanks for your advice.