I'm trying to screw in a new overflow plate to my tub. We recently bought this house, and it didn't have an overflow plate at the time. I tried to screw in the new plate, but about halfway though it started spinning freely without going in. It won't unscrew either: just spins freely. How can I fix this?

I've tried screwing and unscrewing it, with normal amounts of force and as much as I can apply. When unscrewing it, I tried pulling on the plate.

I looked at the plumbing behind the wall(there's an access panel) but that was unilluminating.

Here's a video of me trying to unscrew or screw in the plate.