It’s the little door that flips open when you insert the key. Get a thin ice pic paper clip or tiny knife blade and coax it out. It’s not that hard
This. The metal rectangle covering the slot the key goes in is spring loaded. Over time the spring can fail or the metal door break and little bits get lodged in the space the key goes. Get a paperclip, thin ice pick, SOMETHING to fish out the bits and you should be good to go...
(Stock image, not a Valk)
