Why does my amaryllis not change?

Honestly, I’ve been meaning to look up a little care and feeding information, but it’s been months, and I have not. I rescued it, put it in a jar of water, and kept the water full. As near as I can tell, it’s changed about as much as a plastic one would.

It’s a large beautiful green fan that just sits there. no growth, no blossom. Winter is coming on, and I don’t want to watch it slowly peter out.

Give me a clue?