Turn off the firewall. Use this free service https://www.grc.com/x/portprobe=3389 to "probe" your ports. It should say your port is open. Then turn on the firewall, and rerun the test. It should still be open.

If the test says it is closed, you have a problem. I have a "smarter" router. The port stays closed until a program requests it. For example, my port xxxx is open on the router, but it is "closed" to the probe. When I start my uTorrent, the port automatically opens. This may be your problem. I had problems using Wake on Lan over the internet because of this stupid behavior. The workaround was to use Intel Active Management (its an always on webserver, even when shut down) to trick the router into opening a port.