How to handle receiving a [Mobile Publisher Action Required: Invalid Login Credentials] email for Mobile Publisher (iOS)

This knowledge article is intended for customers who have subscribed to Mobile Publisher and are submitting an application for iOS. It is also intended for customers who have received the above email.
If you receive this email, additional action will be required in App Store Connect.

Apple logs in to your Experience Cloud site as an Experience Cloud site user to verify the app's functionality. Therefore, you will need to provide the test user credentials for logging in to your Experience Cloud site in App Store Connect.
Please note that if you have IP address restrictions or MFA enabled, Apple may not be able to log in, so it is recommended to disable these features.
In addition, if the password of the user listed in App Store Connect is changed on a regular basis, you will need to update the test user's password in App Store Connect.
If both of the following conditions (A) and (B) apply, please include a note in App Store Connect along with the user's login credentials, stating that the information is for logging into the production environment.

(A) In the Salesforce settings ( [Setup] > [Mobile Publisher] > [Target submission details] ), the [Sandbox Site] field has been filled in with the URL of  Sandbox org.

(B) The user credentials entered in App Store Connect belong to a test user in the production environment.