High beams no longer working

Around 6 months ago I realized the high beams on my 2013 Prius Three weren't working. I pulled the fuses and they looked fine, just a minor bit of corrosion on one of the 10a ones. Bulbs looked okay, but went ahead and replaced the drivers side with a spare to see if made any difference, and both bulbs started working fine.

They've since gone out again. I replaced the bulbs again with new ones but no luck. I also tested the following with a multimeter:

* 0v in the driver side bulb harness (forgot to test the passenger side)
* 0v in both of the 10a H-LP RH HI and H-LP LH HI fuses. Tested both sides of the fuse and neither showed anything
* 13v in the 20a H-LP HI MAIN fuse

I replaced the 10a fuses just in case something weird was going on but that didn't make any difference, and still show 0v on both sides. The blue indicator light on the dash is still on.

I'm guessing this means there's a short somewhere between the battery and the fuse box. Has anyone had any experience with troubleshooting this further?