I too am seeing a new behavior with iOS 15. Prior to iOS 15, I would use Sandbox testers with TestFlight builds for IAP renewable subscriptions. When making the IAP purchase, I would be challenged (in a modal dialog) to enter the Sandbox testers credentials (both username and password). Sometimes, I would be challenged to re-enter the password to complete the subscription. This has not changed between iOS 14 and iOS 15 devices. However, if I then delete the app, reinstall from TestFlight and attempt to restore a purchase, on iOS 15, I am getting the error "An unknown error occurred". I was able to inspect the console logs and found these entries default 12:16:37.428196+0100 SubscriptionApp -[EBAuthenticationService paymentQueue:restoreCompletedTransactionsFailedWithError:] [Line 599] ERROR:Restore transaction failed: An unknown error occurred { NSLocalizedDescription = "An unknown error occurred"; NSUnderlyingError = "Error Domain=ASDServerErrorDomain Code=1001 \"MZFinance.NoAccount_message\" UserInfo={NSLocalizedDescription=MZFinance.NoAccount_message}"; } It seems appstored looks for a different account that what we have setup on the device settings. default 12:16:12.627633+0100 appstored AMSAuthenticateTask: [53574A61] Looking for an existing account. altDSID = (null) | DSID = (null) | username = (null) default 12:16:12.630357+0100 appstored AMSAuthenticateTask: [53574A61] Failed to find an existing account. We'll create a new one instead. default 12:16:12.643095+0100 appstored AMSAuthenticateTask: [53574A61] The device doesn't have an active account for com.apple.AppleMediaServices.accountmediatype.appstore.beta. We'll make the account active if we successfully authenticate it. error 12:16:12.643619+0100 appstored "Error returned from daemon: Error Domain=com.apple.accounts Code=6" default 12:16:12.643923+0100 appstored AMSAuthenticateTask: [53574A61] Generating a password. default 12:16:12.644018+0100 appstored AMSAuthKitUpdateTask: [53574A61] === Starting === And after signing in with the sandbox account: default 12:16:35.308770+0100 appstored AMSAuthKitUpdateResult: [53574A61] AuthKit gave us updated identifiers. We'll attempt to find an existing account that matches the new identifiers. default 12:16:35.309871+0100 appstored AMSAuthKitUpdateResult: [53574A61] The new identifiers are for a different existing account. existingAccount = <ACAccount: 0x10870a900 type = iTunesStore.sandbox | backingID = 1B413FC4-01CC-4DF0-B7B5-8331500E02A3 | username = qa-eb01@cliqconsulting.com | altDSID = 000722-10-7e386279-e9bd-4bad-98c6-6493494087cc | DSID = 20457517352 | active = true | storefront = 143441-1,30 ab:aF574PC1> default 12:16:35.312802+0100 appstored AMSAuthKitUpdateTask: [53574A61] The AuthKit authentication succeeded. result = <AMSAuthKitUpdateResult: 0x108d5fbd0> default 12:16:35.312855+0100 appstored AMSAuthKitUpdateTask: [53574A61] === Finished === default 12:16:35.313213+0100 appstored AMSAuthenticateTask: [53574A61] Successfully generated a password. Performing the authentication. It appears that iOS 15 no longer allows the use of Sandbox Testers for IAP with TestFlight In the Settings app, under App Store, there is a new message showing on iOS 15 SANDBOX ACCOUNT This account will only be used for testing your in-app purchases while developing locally. Your existing App Store account will be used for TestFlight apps. Are TestFlight builds now required to use production Apple ID accounts (and not Sandbox testers)?