Reason for app rejection: Issue - Need login credentials for app review

In order for us to review your app for compliance with Developer Program Policies, we will need you to provide valid login credentials for your app. 

If you previously supplied credentials, please ensure that they have not expired. 

What does it mean?

Google tried to access the app using the provided demo account but unsuccessful to login.

How to resolve it? 

Check if the provided login credentials are valid

• If Yes, ensure that there is no space/s in the username and password fields.
  You can also add a note (for the Reviewer) saying that the credentials are working.
• If No, provide the correct credentials.

Once updated, click Apply, and Save. Then, resubmit it by going back to Main/First screen > click the app > click Go to Publishing Overview and there you'll find the blue button Send for Review. 

Click it, and it will be resubmitted with the same build.

Do I need to generate a new build?

No.