Here's a link to the update for easy reference.
Quote:Spartan Assault & Spartan Strike - There is a compatibility issue for “Halo: Spartan Assault” and “Halo: Spartan Strike” on Apple devices running on iOS 10+. We're preparing to temporarily remove both games from the Apple App Store while we work with our partners on a software update. We apologize to players who are unable to play these titles and are working to get both games back in working order as soon as possible. We'll provide additional updates in the near future as plans progress.