Though a garage door system isn't very complicated, but when your garage door stops opening when it should, there are several different possible causes. Making sure your garage door opener has power, that your remote is synced, and that any broken or damaged parts are fixed can resolve your problem with little trouble.
Remote Isn't Transmitting
There are a few reasons your remote might not be transmitting properly. The battery could be dead, or there could be so little power remaining that the transmission isn't strong enough to reach the receiver unless it is very close.