So I’ll update.
Pulled both ballasts and switched them. The problem followed the new ballast. Hmm. Seemed like a defective new ballast.
Then just for fun I put the old “bad” passenger side ballast in the driver side and both lights came on!? After some inspection of the new ballast it seemed like it wasn’t making good contact. It didn’t click in like the existing ballasts did. It wasn’t oem but just didn’t feel right on entry.
My only guess is that maybe the previous ballast wasn’t making good contact anymore? Either way, the solution was switching the passenger and driver side ballasts.
Things work. I’m happy.