The problem is the MQTT version in the marketplace. Got the same problem with TWX7 and disconnects.
You have to DELETE the old extension and import the new one you get here:
I was not able to make an update. It told success, but did not solve my connection problem. Now it is running fine.
I'm the creator of the ActiveMQ Extension and I wanted to jump in to bring more information about it.
The ActiveMQ Extension only supports the JMS specification (meaning no MQTT or AMQP).
This information is present also in its user guide.
So, in order to connect to an MQTT broker, you will have to use the MQTT Extension only.
Hope it helps,