User Profile

We are trying to use new beta api: Get Transaction History(https://developer.apple.com/documentation/appstoreserverapi/get_transaction_history). And the first step is to generate an in-app purchase key on App Store Connect -> Users and Access -> In-App Purchase. But after generate the key and click download, it show up "An error occurred, please try again later", and we can not do it because it is an one-shot download. it works fine on old type key of "App Store Connect API". We have tried to switch to different browser or admin user. on Console we found that the request for downloading key returns http error code 410 (https://appstoreconnect.apple.com/iris/v1/subscriptionKeys)

At ASAuthorizationAppleIDCredential, we got the Unique, Stable and team-scoped User ID, which allow us to identify users from different applications under the same developer account.But, we are also allowed to transfer an app to another developer account.If it is the case, what will happen to the User ID?Will the User ID change? Will it be different from the other Apps under the new developer account? Or other changes may occur?