Cannot subscribe to messages

[javirs85]

I use a 3rd party broker app (because I'm unable to connect to the server here)
https://play.google.com/store/apps/details?id=server.com.mqtt&hl=es

I connect to the broker correctly from C#, and from a nodeMCU device running micropython. I can submit messages from both python and C# but I only receive them from python. The subscribe method never reacts.

Here a question in stack overflow I posted with slightly more detail:
https://stackoverflow.com/questions/54768813/xamarin-mqtt-not-subscriving-to-messages