See if the opener's cord is plugged into a working outlet.
make sure that the lock feature is turned off (this may cause the opener to not espond, not because it is broken, simply because it is instructed not to perform!)
Try unplugging the garage door opener from the socket it is currently plugged into (this just like a common restart done with a non responsive personal computer, and may solve te need for calling a garage door opener repairman or company, this sometimes does the trick by resetting the sensors).
Make sure your opener's remote control batteries still have power, and better yet, replace them with new ones and test your garage door opener again.
If there's no problem with the batteries, the remote may have been reprogrammed - so simply contact the manual provided with this specific garage door opener or consult the manufacturer directly.
make sure the beam sensors are plugged in.
Garage Door Opener Sensors
Clean the sensors eyes from dust or dirt accumulated over time with a wet piece of cloth (sensors are usually located in front of the "on / off" button). Try to clean these sensors every season - this may help this issue from not reoccurring for a long time…
Check to see if the chain is broken or loose. if it is broken or needs tightening you'll need to contact a garage door opener repair company or an electrician to do the work without damaging the chain or any other important part of your garage door opener operating system.
if nothing seems to work, pull the red release cord that frees the door so it may be opened or closed manually. Older systems may not have a red release cord, but may have a button or handle to serve the same purpose.
Consult your owner's manual - you may find valuable information that in turn can save you time and money handing this costly equipment safely.
Note: Working with electricity is very dangerous — be extremely careful and, if you have any doubts, contact a professional.