We’re hearing from some people who have upgraded to the latest iOS app that they’re having a few problems. Here is some advice to help you settle in, as you get used to the updated app.
ATLAS purchase
Some people are reporting that after updating the app, they’re being prompted to purchase ATLAS again.

No need to fear; you do not need to buy ATLAS again. Just take the plunge, and click Buy! You will not be charged again. You’ll see a message like this, though:

After you tap OK, ATLAS will be back to normal.
Tip: Did you know that you can re-download Halo Waypoint on as many iOS devices as you’d like (your iPad, your iPhone, your iPod Touch)—and if you’ve purchased ATLAS once, you get it everywhere at no additional charge?
Challenges
Some players are having trouble finding Challenges. In the latest update, we changed the Challenges button into a Waypoint button, so that it would be easy to get to the latest news as well as the forums. But Challenges haven’t gone away!

Just tap Service Record, and then tap Challenges.

Please visit the Halo Waypoint section of our forums if you have additional questions!