In my bathroom the existing gfi outlet tripped and would not reset. I figured it was gfi problem and bought new one. It is a 20 AMP outlet. I installed acccording to installation procedures and have a solid red light on GFI and button won't stay in to reset. This is a four wire setup with a load and line. Tried disconnecting different things on circuit and no joy? What is my next step? Meter?

Meter or test light will verify you have the HOT side going to Line, Indicating light will also tell you have Power. Remove Load side and try to reset, If it resets, then problem is on Load side, and GFI is OK. Unplug or disconnect anything on the load side, try again.