One of four outside light fixtures (all controlled by same switch) isn't working and it's not the (3) bulbs
Check the voltage at the fixture that isn't working, it could be a bad connection there. If there is no voltage in that box, go to the next fixture box, which is working, and test for loose connections there that would affect the feed to the fixture not working. If there is voltage there and all connections are good, look for a break in the wiring between that fixture box and the fixture box not working.