25 challenges completed, but no achievement

Games Other Halo
1

My service record shows that I have completed 25 challenges.

But the achievement “The Challenger” has not unlocked.

I see this glitch is a common issue, with some players reporting 50 or more challenges and no achievement.

2

Mine popped on the 28th challenge, so just keep doing them and it will pop eventually!!

3

Yep mine popped on 26.