Monthly subscriptions immediately fail with "purchase cancelled" while yearly subscriptions work fine

I'm experiencing an issue where monthly and family monthly subscriptions fail immediately with "purchase cancelled" in TestFlight, while yearly and family yearly subscriptions work correctly.

Setup:

• All 4 products in same subscription group
• All show "Ready to Submit" status
• Using react-native-iap with StoreKit 2
• Testing in TestFlight sandbox

The Problem:

• Yearly subscriptions work fine
• Monthly subscriptions fail immediately with E_USER_CANCELLED (no dialog appears, user didn't cancel)

What I've verified:

• No active subscriptions (getAvailablePurchases() returns empty)
• No pending transactions
• Same subscription group for all products
• Product IDs match App Store Connect
• Code is identical for all products

Error: E_USER_CANCELLED fires immediately when calling requestPurchase() for monthly products, but yearly products proceed normally.

Questions:

1. Why would monthly fail while yearly works (same group, same config)?
2. Could this be sandbox state corruption for monthly products?
3. Should I delete/recreate the monthly products?

Any insights would be appreciated!