Tranny

So I was driving and my trans fluid was low. About 1/4 of the way full. I lost 2nd I added fluid and it wants to shift but doesn’t shift it’ll get up and act like it will shift I’m no mechanic at all it’s a 2001 Cherokee sport 277200 miles on it. Well kept. Just wondering if the trans is blown or is it a censor? It’s currently down pouring and had to run to the store don’t know if water got to a sensor or not any help would be awesome