I recently had an outlet quit working in my shop. 20A outlet (12/2 w/ground romex) in midstream. my contact tester showed power coming in and going out, but this outlet and 2 downstream were not working. looking closer, the ground screw was a little loose (wire was still in place, maybe a little loose). after tightening the ground screw, all outlets worked. it appears to be wired correctly (black on brass, white on silver), and my little plug in tester also showed that it was wired correctly.