This is probably a dumb question. My house is 20ish years old. I have some old, cracked snap-on wall plates that I'm replacing (these snap-on covers also keep falling off), but the single middle screw on the new wall plates doesn't thread at all. It's not a distance issue since it won't work if I try just the screw without the cover.

The wall plate covers I got from Lowes are Eaton and I haven't pulled the plug to see who the manufacturer is.