I am literally in the exact same situation as you! The only difference is that my Hard campaign achievement progress is stuck at 0/25 now even though I achieved 20/25 in 2010. I even completed the campaign on Brutal recently, but that did not give credit towards the Hard achievement.
This is my request for help.
I even tried deleting the Blizzard cache as suggested by the GM in my post, but that didn’t fix it.