Are you running the microflow that subscribes to the MQTT server in an After Startup action? If you are not, I suggest moving it there. Also look at putting the MQTT Unsubscribe action in a Before Shutdown action.
Another thing to check is what server are you trying to subscribe to? If it’s test.mosquitto.org I’d suggest looking at iot.eclipse.org instead as it’s more stable.
Finally, are you seeing anything in your logs relating to MQTT?
It worked, in the end I was showing the values on a data view, when I changed to data list, it appeared all the data.
But now I'm trying to send a JSON but I'm not being able to set parameters to the export map, it's appearing some error. Do you know what can I do to fix this?