Rejected — Guideline 3.1.1: digital goods sold outside In-App Purchase

The app unlocks digital content/features via Stripe, PayPal, a web checkout link, or by telling users to 'visit our website to subscribe'. Apple requires StoreKit IAP for digital goods consumed in-app. (US storefront exceptions exist post-Epic v. Apple via the External Purchase Link entitlement, but they are narrow, US-only, and have their own rules — don't assume they cover you.)