Try connecting internally using.. inside IP address's.. (meaning log on to your wifi)
Then find our wan IP and try that IP address.. (assuming your doing for DDNS)
You can use a simple command
telenet ipordomain 3389 to see if the port is open and/or routed correctly..
Troubleshooting requires conducting tests to see what is causing the problem.. the problem can only be your computer or router.. inside test proves computer is fine.. outside test proves it's most likely the router..
inside tests work fine. When i turn off wifi and try with my external ip, or anything else for that mater. I get a sprint conection error not a rmd error I think i must have a setting on the phone wrong somewhere, because it keep refering me to my network settings on the phone...