Advanced Commerce REACTIVATE_SUBSCRIPTION intermittently fails with StoreKit.InvalidRequestError code 1

Hello,

We are using Apple’s Advanced Commerce API and are seeing intermittent failures when reactivating a subscription from the app using REACTIVATE_SUBSCRIPTION.

Reproduction flow:

1. Purchase a regular StoreKit auto-renewable subscription.
2. Migrate the subscription to Advanced Commerce.
3. Disable auto-renewal from Apple’s native subscription settings.
4. Return to the app and try to reactivate the subscription from our subscription settings page.

This exact flow was working successfully few days ago. The payload structure has not changed, but the same flow now sometimes works and sometimes fails with:

Error Domain=StoreKit.InvalidRequestError Code=1 The operation couldn’t be completed. (StoreKit.InvalidRequestError error 1.) userInfo=[:]

We reproduced this with a newly created Sandbox Apple Account and a newly purchased/migrated subscription.

Questions:

1. Is there a known issue with Advanced Commerce reactivation?
2. What does StoreKit.InvalidRequestError code 1 mean in this context?
3. Is there a way to get the underlying rejection reason?

Thank you.