I've had this same issue..... cupholder stuck and I'm thinking, "What the"!!!

As you're sitting in the drivers seat, use your right hand and first push in the expandable flaps that are towards the front (engine) side of the holder. If they were extended, they will move about a quarter inch into position. Next, pinch the rear top part using your right thumb and forefinger. (Your thumb will be inside the holder area, and your forefinger will be against the silver portion.) As you pinch this section together, gently fold the cupholder down into the closed position.

After a few "What the's", I figured out that I needed to be gentle with it or risk breaking it.

If this doesn't work, then I think you're correct in thinking that you have a stuck up cupholder..........this could happen if not used daily and it's become sullen and moody.