Digital content not using In-App Purchase
App sells digital content, subscriptions, or unlockable features through a third-party payment system instead of Apple's In-App Purchase. This is the core IAP rule — digital goods must go through Apple.
31 cases reported · ~11 days to resolve · 0% appeal success
Apple's rejection message
Guideline 3.1.1 - Business - Payments - In-App Purchase: Your app offers digital content or features for purchase but does not use in-app purchase, which is required for digital goods and services.