Terminal Services Connection error

I help administer a network at a doctors office. They use Terminal Services to pipe in from home and the hospital. They use it in the office for a particular program. The problem is that anyone that has rights to login to terminal services can from outside the office, but on the LAN all clients get a unable to connect, server is busy. I tried to go through there router with a static ip address to simulate those from outside the office but same error occurs. License are an issue but apparently not for those outside of the office, but that will be resolved soon. Outside of licensing is there anything that I am missing?