We're excited to announce that we've fully migrated the Xbox Forums to their new home, here on the Microsoft Community forums!
As of today, going to forums.xbox.com will redirect you here to the Xbox area of the Community forums. We've moved all of your existing threads over so you can continue and start conversations with the new forums experience.
We sincerely appreciate the feedback you have provided over this transition and can't wait for you to check out the new Xbox Forums!
This happens to some people. Are you sure you finished every level on vet? Make sure you double check on the level select screen. I typically play the missions in order, but from what others say you can do them out of order and still get the achievement.