Headlight not working

I have a 2017 tlx and when i open the door to get in the car both headlight lights up, but when i start the engine the driver side headlight low beam dont work, but both high beams work, i found no explanation on the internet so did this ever happen to you and if yes what was the problem, i tried switching both sides fuses and it didn’t fix the problem, knowing a whole headlight assembly is 800$ +, i would like to know if there is an easier fix than replacing the whole unit