the hinged floor plate does not close , it was ok but suddenly doesn't lock in place. any suggestions?

I would start by removing it from the stock if you haven't already.

If the fault really is "sudden", look for simple reason. Bent or broken locker tab on plate, need lube on moving lock mechanism, something foreign impeding full closure of plate, etc.

If I had to guess from your pic, it looks like your floor plate has a bind somewhere. Where the rear screw is the floor plate goes beneath the stock and where the front screw is the floor plate is flush with the stock or hanging a little out of it, and its not letting that catch right when you close the floor plate. Check your screws also. The rear screw is below the floor plate and the front is flush, check your magazine box.

It needs a small flat washer between the stock and trigger guard assembly rear bolt hole. . The trigger guard assembly on my six Rem700's always sits slightly proud - yours is sitting below flush.

I might be completely off base but I have about 15 Remington 700s and most have been customized. Looks like a custom (after market) stock to me. Is it possible the stock is preventing the floor plate from closing? Trigger guard assembly is below flush as dingo stated.

As has been said you need a shim under the back of the floorplate

I vote for this one.

I’m also with using the flat washer. Just had this same problem with a Model 7 and aftermarket stock. Added the washer and everything is good.

All good advice sometimes a drop of oil and freeing a sticky mechanism by working it back and forth.

after removing it snaps in place , same issue when i put it back.

This should fix it.

i have millions of washers when i don't need one. now i have to go to home depot for one washer.

Probably try a little redneck engineering and figure something else out to work as shim, at least for the meantime and to verify that it fixed the problem (which it sounds like it should).

i did , seems to work.