Hi again,
We were facing with kinda same situation. We are not able to cancel our subscriptions which made in TestFlight.
We cannot cancel it from Device > Settings
We cannot cancel it from Apple Website
We finally found out that you have to call
await AppStore.showManageSubscriptions(in: windowScene)
This method presents a sheet to manage your subscriptions.
Note: you have to be in correct sandbox account before presenting this page. You can change it from Device Settings > Developer > Sandbox Account
Hope this helps.
Topic:
Developer Tools & Services
SubTopic:
Apple Developer Program
Tags: