DIAGNOSIS Ten flashes on the main unit's lights means the travel limits are lost. The opener doesn't know where 'up' and 'down' are anymore, so it refuses to move to keep from driving the door into the ground or the header.
FIX You'll need to reprogram the travel limits. 1) Pull the red emergency release cord to disconnect the door from the opener. 2) Manually lift the door all the way to the fully open position. 3) On the wall control panel, press and hold the 'door' button until the opener light blinks. 4) Press the button again to lower the door. The opener will relearn the down limit. 5) Press the button a third time to stop it. 6) Reconnect the door to the trolley by pulling the red handle toward the door.
IF THAT DIDN'T WORK If the door moves erratically or the limits won't set, the force settings might be interfering. Try resetting them first: on the back of the wall console, there are small up/down force adjustment dials. Turn them both down to the minimum setting, run the limit reprogram steps above, then adjust the force back up just until the door reliably opens and closes.
HEADS UP When the door is manually disconnected, it will fall freely if you lift it. Make sure you have a good grip and nobody (especially kids) is under it.