Have you checked your fuses? Your owner's manual should have a chart to guide you to the right one to test. Use a continuity tester if you have one. If the fuse is good, then you want to get a test light to determine if there is voltage to the connector in back of the headlamp when low beam switch is on. Do those two tests first and then get back to us.
I would go next to the headlight relay. I'm not an automotive electrical, so I'm just throwing out the more obvious possibilities. Sometimes, if you can find another relay in the relay box with identical part #s, you can do a swap to see if that was the problem. You can also learn how to test relays on YouTube:
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