A check for HBO Max
Before resetting a password, check the issuer named on the receipt and the sign-in choices shown by the app. If your subscription comes through another billing partner, use its documented account linking steps. Give support the issuer and error stage without sending the receipt number publicly.
Check on the intended screen
Open the app catalogue on your actual device and confirm the publisher and region. Sign in only through the service or documented billing issuer.
Keep a title-level test
Use one title, episode or fixture that you can identify. Record whether the app launches, the account signs in and the item plays.