Those things work with or without a ground. It could be nuisance tripping, it happens with anything. If that is the case it is defective. To be sure disconnect the load side and see if it still trips.

If it does and there is nothing plugged into it, it is bad, if it does not trip, it is something off the line coming out of it that it is supposed to protect, and actually is probably doing its job.

The way to find out all what runs off it is to disconnect the OUTPUT neutral and with the branch circuit turned off, go to every neutrl around. I have wired them to protect lights, you have to for the over the sink lights. In some places you can't even do that, you have to install a GFCI breaker and run all new to the kitchen or sometimes bath. The NEC does ot necessarily require it, but some rehab codes do.

But who cares. You want the thing to work.

Take the load off and see what happens.