TRYING TO HELP A NEIGHBOR WITH A CHAMBERLAIN GARAGE DOOR OPENER, MODEL 12456MR, SERIAL# 20206C00296. WAS WORKING FINE TODAY AND WENT TO CLOSE IT AND WOULDN'T WORK. TRIED THE 4 BUTTON EXTERNAL AND WIRED INSIDE BUTTON. LIGHT COMES ON AND LIGHT NEXT TO THE RE-SET FUSE ON THE BACK BLINKS, BUT THE OPENER DOESN'T DO ANYTHING. I UNPLUGGED AND PLUGGED IN AGAIN, BUT NO HELP. ANY IDEA'S? IT HAD WORKED UP TO TODAY. TKS, RANDY