Check for a loose wire going from the circuit board to the light
socket.

If it's not obvious the best way to tell is w/ a volt meter on what is
wrong.

Sounds like the light relay is pulling in (the loud click) so the
points on the relay could be dirty. With a volt meter you can measure
if there is 110 vac coming out of the circuit board to the light socket
wires. If you can't measure any voltage or low voltage it's most likely
the relay contacts.

If there is voltage coming out of the board check for voltage at the
light socket where the wires connect. If there isn't voltage the wire
is bad or there is a loose connection in the harness to the board.

If there is voltage the problem is in the socket(s). You may need to
clean the contact point (w/ unit unplugged of course) or bend the tab
upward slightly to make better contact w/ bulb. If they still don't
work replace the socket(s).

Doordoc
www.DoorsAndOpeners.com