Hello dear,
If you bubbled the wrong roll no# or incorrectly, chances are that the system didnt recognise your roll no#. And so the omr sheet might not pop up with your login credentials.
You can also go through NTA helpline number.
Email :-neetug-nta@nic.in
Phone number :- 8076535482, 7703859909
thankyou
Feel free to ask your further queries if any.