Jadnashua
Retired Defense Industry Engineer xxx
At least you could quickly determine where all of the working circuits go, which may narrow it down some. Sometimes, a good visual inspection is all it takes. If there's a broken wire somewhere in the wall, or say one that got punctured by a nail or similar, it's harder to trace. I'd first remove the wires from the load side of the GFCI, and verify that the GFCI doesn't start to work. If everything downstream from the GFCI is not working, I'd definitely start there! You never did verify that you pressed the reset (it should click going in if it is tripped), and the test button actually does something. That receptacle will NOT work if it is either defective or tripped. I had an intermittent connection that gave me fits...I isolated it as a run between two receptacles on the chain. I eventually just ended up running a new cable, since I wasn't going to tear the walls apart to find out what the problem was in between.