Before re-seating the headlight assemble into the wiring socket on the tray tower, I'd suggest doing several things. First, inspect the socket to see if the clip holding it to the tower is in good shape. If it's broken or cracked, the socket may move too much when re-seating and not allow for a good electrical contact. Second, try cleaning both the blades and the socket receptors with electrical contact spray to make sure everything is clean. This may also provide a bit of lubricant when re-seating.
If you do these things and the lights still don't work, then its probably time to get out the voltmeter and make sure you have power to the socket. Here's a link to pin diagram for the socket.
FYI: headlight connector pinout.
If you have power and your confident the headlamp assembly is working, then its back to finding a good electrical connection. You might have to take off the fender liner and push the socket onto the headlamp plug to get things firmly seated.
Good luck