So I have this relatively new (2-3 yrs) Liftmaster Elite garage door opener that has worked fine until today. For no known reason, it doesn't want to open or close when I push either a remote or the wall unit. Then, when I come inside the house, it does something. At other times, just when I think it is working, it goes down 3/4 and then stops. I checked the sensors, and they seem secure, with nothing in their paths. Any ideas would be appreciated; certainly don't want to pay someone half the cost of the thing to come out and do a simply adjustment.