Driver low/high beam issue
 

I'm driving an 05 Monte Carlo. The vehicle is new to me, so I don't know much about it. I'm having an issue with the high and low beam on the driver side. The blinker and park lights both work. Every other light on the vehicle works. I've taken a light tester to the wiring harness, the sockets for the bulbs, and tested the bulbs. Everything works. Does anybody have any experience with this issue?

What exactly is the issue? I might have missed it in your description.