Ok folks, lets get right into some issues which you may find once you get your pool cover off the pool and go through some trouble shooting steps.
1. Water level is low to non existent: 1st make sure your pool cover didn't have holes in it and you didn't pump your water out of the pool when you were pumping water off the cover. If this isn't the case and you lost a large amount of water you most likely have a hole in your liner or split seam. Liners without water is not a good thing as they tend to shrink and once you refill the pool the liner can break free from the coping or bead lending itself unfixable so if you have an older liner I would suggest calling in a pro to give you suggestions even on a newer liner I would call and ask depending on your given situation and water level.