Using new iPads, newly set up Apple Business Manager, and subscribing to a new Apple Business Essentials with new users, I can not get a device to allow login. What am I doing wrong?

I've gone back and forth trying different methods with different users but the same results. I get the following: "Apple ID can't be used in this Store" and "This Apple ID is associated with Apple Business Manager." To which, yes, of course it is, Apple! I'm trying to use one of the users that I created with your management software to login to a managed/authorized device set up within your same software with your business subscription.

If I try to "Go to Apple Business Manager" after it fails with the previous attempt, it just goes back to the main Remote Management screen with my org listed and adding "Authentication Failed." I have read many of the Apple documentation entries and tried searching Google for similar issues but have not found an answer.

Can anyone that has more history setting this type of thing up please give me a hand? Humor aside, I really need to get the 6 new iPads my company recently purchased set up for users we are able to manage.

Thanks so much