Help! A drawer lock on my vintage sideboard will not unlock. :(

I have never had this problem before. When trying to get to some of my silver to use on my Thanksgiving table, I cannot get the bottom drawer of my sideboard to unlock. I've tried everything I can think of. And, no, I cannot get to the drawer by opening up the one above it. There is a skirt board between drawers.

I've posted on two other boards, as well. Hoping someone can help or make a suggestion.

Below are photos, including one of the lock (from the above drawer) and of what the key looks like. Apparently, the lock bar is stuck in the upright position. However, the lock turns all the way, just like the others.

Oh, hard situation.