I have a newly built and wired shop with 3 power circuits for outlets. Each circuit (call them A, B, C) is protected with a GFI at the first outlet and all subsequent outlets on that circuit is on the "Load" side of the GFI.
The GFI on circuit A tripped a couple weeks ago. Nothing is plugged into that circuit. I tried to reset it but it won't reset. I disconnected the Load on the GFI and checked the Line power. It is powered, there is no load, but it still would not reset. I replaced the GFI thinking it was bad and a week later the same thing happened to the replacement GFI!
Yesterday, I pushed the test button on the GFI on circuit B. It tripped the GFI but when I went to reset it, it wouldn't reset. So just as in circuit A, I tried disconnecting the loads on the GFI, made sure it had power on the Line input, but it still would not reset!
Since this is going on with no Load on the GFI, and nothing is plugged into any of them, it is not due to an actual ground fault. (I also checked for downstream ground faults with an ohmmeter and found none.) There is something weird with the wiring between the GFI and the panel, I believe, that is possibly frying the GFI's internal electronics. Perhaps the ground and neutral are not properly connected at the main panel?
BTW, all the work was done by an electrician. He was not sure what is going on so I am sleuthing a bit on this also.