Weekly Challenge Not Registering?

I completed the weekly challenge “Infinity and Beyond” but it says I have not completed it. I did the mission on Legendary with all 4 specified skulls active (Even on my service record it shows I completed the mission “Infinity” on Legendary) But I have not earned any experience and it still says 0/1. I can play on multi-player perfectly fine, I’m connected to XBOX Live fine yet the challenge is not completing. I’ve tried resetting internet and my Xbox. Still nothing. What’s the problem?

Did you play the mission from the very beginning?