I had this a couple of months ago. First place to check is the loom that plugs into the headlight. Remove the headlight and check the cable for any and all damage. For me, the cable was fine.
For the headlight, the prospect of putting it in the oven, removing the lens and then working around the inner workings seemed a little too scary. Instead, I used a soldering iron with a knife attachment to cut a hole into the black casing, found the problem (caused by the ball-joint coming apart).
I pushed the joint back together, and use the soldering iron to 'weld' the plastic hatch back into place. Not the neatest of job, but far simpler than cooking the headlight!
Few photos here...
https://photos.app.goo.gl/mGjCLbdx2WEWGr8K9