Simple, but yes, change the bulb – please note that only regular incandescent light bulbs should be installed directly into the motor unit.  Florescent and LED bulbs may not insert to the proper depth, and also may interfere with the signal from your wireless devices (remote controls, keypad).  If an incandescent bulb still doesn’t work the light socket can be replaced in Chamberlain/Lift-Master motor units.  If you’re a DIYer it’s not difficult to replace the socket yourself if you’d like to pick one up from our shop, otherwise please contact us to set up a service call.