Chances are that the plastic tube connecting your tub to your water level switch has been eaten by rodents :-( - hopefully, that's all they've dined on. Post a make/model/serial number and we can give you some help.
Thank goodness rodents weren't the problem! The hose had come loose (probably when my husband was moving it). When he took the back off the washer and reconnected the hose, it worked perfectly. Thanks for your help!