Well the answer to this one is really obvious.
The wiring has a broken connection somewhere inbetween the microswitch and the board.
Use your multimeter (which I am betting you don't own, go buy one right now, most important tool in this hobby), to check the connection between the microswitch and the appropriate pin on the edge connector.
If you have continuity THERE, then that pin is no longer making a good connection, so get something small and bend up the part that makes contact with the PCB and see if it works then.
If you DON'T have continuity there then the connection is broken somewhere between the edge connector and the microswitch. Examine the wiring for breaks. If there is another connector inline then that is likely the problem, see if it is making good contact. If that is the problem, and you don't want to replace the whole connector, then simply splice that wire AROUND the connector.