I got it to work

 I managed to bypass it and login

hope this helps.

Just sign with your AT&T account credentials even though it shows up as DirecTV login after you click the AT&T provider option. 
it’ll tell you they can’t find the account bc you obviously don’t have DirecTV but click “forgot my password” and go thru the steps- it will send you an email and have you change your password to yourAT&T account- go thru the steps and it should push you thru the HBO Max app