"You are missing packages that are essential to run Microsoft Flight Simulator"

I tried everything this article mention but still got the same results. I, however, found what worked for me. I deleted everything in the OneStore folder and came out and back in again. It rebuild all the packages with around 135 Gigs of data and then came up like a champ.

If you are out of ideas go for it. I did put everything in that folder in a backup folder on my desktop in case I screwed things up, I recommend that you do the same just in case.