If the software is blocked to send outgoing messages, then you cannot send info to the server.
The latter happens for many reasons. Sometimes an aggressive antivirus program, sometimes because you are not an admin user, sometimes because you have a router setup to block all requests outgoing on port ###, lots of reasons.
I will try to get you a raw http request string that you can paste into a browser window to simulate MDX talking to the outside world. If that works, then you know it is something on the PC blocking it. Windows Defender is pretty aggressive unless you tell it not to be for certain applications.