I'm afraid to say it sounds DOA. You should contact the people you bought it from and explain the problem to them.

This is one of those things where if you have to ask how to fix it, you can't In other words, unless you're a whiz with the inner workings of electronic gadgets, it's a pretty safe bet you won't be able to trace out and fix what is wrong. You could open the transmitter case and look for obvious things like loose/broken wires, but that could void any warranty on the plane.