It's certainly not unheard of for a GFCI to fail, but nuisance trips can also occur when moisture is present and causing a high resistance short. Extending the receptacle from the junction box and disconnecting the LOAD side wires will help you determine if the fault is there or downstream.

If the GFCI doesn't re-engage when pressing the reset button, it's likely toast. It happens.

Update: The original GFCI receptacle has two green lights, which were on, confirming that there was power to the device. I purchased a new one, yesterday, and I had a little difficulty selecting the best one. I wanted one which is labeled WR (Water Resistant), because this is outside, in a waterproof cover. Since my primary use for this receptacle is for a level 1 EV charger, which draws 12 Amps, I wanted a 20 Amp one. My store is Lowes, and it appears they have changed their stock in the last month or so, only carrying Eaton brand, and they had lots of them, but finding a WR 20 Amp was difficult. With the help of an associate, I did find one and now have installed it and it works.

One question re 15 vs 20 Amp receptacles. Most (if not all) are labeled 20 Amp feed through, even if they are only rated 15 Amps. Is the only difference that the 20 Amp ones have one T-shaped slot?

I assume that the outlet that wouldn't reset was wired correctly - I think a bad ground might cause it to fail the test.

Does your EV charger have a 20 amp plug? If not, a 20 amp outlet isn't going provide any advantage. And I assume that this is on a 20 amp circuit with 12 gauge wire.

To answer your question - yes, I think the only difference is that the 20 amp outlet has a "T-shaped slot" that can accept either a 15 amp or 20 amp plug. Either can be used on a 20 amp circuit.

Thanks for your quick response, Dennis. Part of my thinking is that perhaps the next EV I get might be able to use closer to 20 Amps, but my guess is that the car marketing would rather have their cheap charger run on a 15 Amp circuit. Regarding the grounding, the ground wire from the panel is attached to the green screw on the metal box, but I'm assuming the receptacle is grounded through its tight mounting screws.

There is no problem with a 20 amp outlet on a 20 amp circuit. Yes, I would assume that car manufacturers would not want provide 20 amp chargers that would require upgrading common 15 amp circuits. If you you have to rewire it's probably worth the added cost to go to a 240 volt circuit - and get a 500% increase an capacity vs. the 30% increase that you'd get going from a 120 volt 15 amp circuit to a 20 amp circuit.

I would not rely on the mounting screws to ground the outlet - that may have been your problem in the first place.