What would cause a GFCI to show no ground with a receptacle tester, the test reset works but an outside source that tests GFCIs does not trip it? I would think that the self TEST/RESET is not a true test of the system. It seems as though the test may work but in reality the GFCI would fail during an actual hazard. The tester works just fine and continues to work so let's not blame the tester.