for the people who aren’t getting the achievements I have a remedy. Now I understand if this sounds strange, however it worked for me and a few of my friends. Go to the level that’s not loading progress on waypoint then (if you already have the achievement for the score/time on the level go to the bottom of this post) beat the par score/time on easy, then redo the mission on legendary and you’ll get a achievement and your progress on waypoint.
For the people who are still having trouble and have the par score/time achievement go to any level that isn’t showing progress on waypoint, set the mission to any difficulty have zero skulls on, turn the scoring on, and beat the mission as you normally would, if you still are not getting the achievements the uninstall the game and try what I previously stated.
I hope this helps, I know it worked for me and my friends. If you need help on any campain list your gt and ill add you and help. I appreciate anyone’s time who reads this!