In App Sandbox does not work IOS Simulator - Flutter

I am trying to test my flutter in app implementation.

In itunesconnect->Users and Access->Testers (https://appstoreconnect.apple.com/access/testers), I added one sandbox user.

Then I launch the IOS simulator from Android Studio. Going through the steps to sign in, I always cant seem to sign in.

Could Not Sign In User name or password is incorrect

See the screenshots - https://i.sstatic.net/IGNS2.jpg

I know the username and password is correct as I am able to sign in into apple id site (https://appleid.apple.com/#!&page=signin)

How can I resolve this sign in problem or what should I do to test (sandbox) in app on ios ?

To test your In App functionality against the In App Purchase sandbox, connect your device to your development workstation then choose iPhone Device as the Active SDK—the StoreKit APIs are not available in the iPhone simulator.

See: https://developer.apple.com/news/?id=08282009a

So in-app purchase sandbox accounts cannot be used on iOS Simulator. You would have to connect an iOS device and link that with Android Studio. In that way, the app runs on a physical device. For this, you would need a Mac. Besides make sure you always take into account the following:

• Always create a test account with an email address that is not associated with another Apple account
• Remove all account details from the test device, before trying to use a sandbox account (otherwise another Apple account might actually be used for the purchase)
• Confirming the email address after creating it might be a good idea (not sure whether that still is a thing, it used to be)