Headlights work on high beam but not on low
Do you have separate bulbs for high beams and low beams? Have you checked the bulbs?
Pyrolord is on the right track. My Highlander has this issue when one of the daytime running lights is out. The bulbs are all interconnected. Look for a bulb out other than the ones you suspect. Circle back if you find the issue.
Within a couple days of finding out one of my headlights’ low beams was out, the other one went out, too. Two new bulbs took care of it.
A faulty multifunction switch can cause the low beams not to function.
Has someone installed aftermarket HID headlights in it?
Replace the bulbs on both side