Hello student I request you to please try once again with the correct credentials your application/Form number must sent to your registered email address and mobile number. Please try to get it from your mail box. In case even after doing all you're not able to download admit card. Please contact NTA immediately, contacts are mentioned below -

Helpdesk Numbers for admit card related queries (Timings 9:00am to 6:00pm, Monday to Saturday):-  011-27667092, 011-27006900 duet@nta.ac.in (mailto:duet@nta.ac.in)

Feel free to comment if you've any doubt

Good luck