GFCI not working, but circuit reads fine?
The best way to see if your circuit to your receptacle is bad is to get a piece of romex and a receptacle and make up a test circuit. If you do this make sure all bare screws and wires are insulated and there is no exposure for electric shock.
Anyway connect the new circuit you just made to your GFCI. If the GFCI tripped then you are making it up wrong. If the GFCI resets then you have a wiring problem in your circuit. It may not cure the problem but at least it will point you in the right direction to look for the problem.