An easy way to eliminate whether it's a wiring or switch problem is, pull the wire off the switch & with ign on ground the wire to earth - the neutral bulb should illuminate.
You could do a continuity check on the switch.
Sometimes the connection just wants a bit of a clean up, I have had success with removing the sealing washer to give the plunger better contact.

In fairness, it's very unlikely that a switch will actually fail.