Really need a pic for proper diag. Wrinkly can sometimes mean it is under hydrated and needs water. More often it is rot. Is it soft, cuz sometimes that also means it is under hydrated but more often means rot. Personally I would pull the whole plant, clean the roots to have a good look. Are they brown? soft? I think more often than not it is rot. I had one that was soft so I cut the roots and they were not rotted. So it was under hydrated. Hard to tell the difference sometime. Look for brown, you can scratch some or the skin off to see the inside better. It should be nice and green and not brown. These plants can go months and then some between watering. I never water more than once a month tops. If you watered and nothing changed its probably rot. Post a pic if you can.