when i try to download my neet 2021 admit card it showing invalid Application no or Date of Birth or Admit card not available y so?

Hello aspirant
Hope you are doing well
First of all don't panic there may be some problem please check all the details carefully and then enter your application no and date of birth in the format (/) this will work .if the same problem occurs again  you can call or mail on NTA helpline numbers and mail adress.
Beside this limited time is left for neet so you should do revision and sample papers it will help you to boost your confidence and secure good marks Below is the link for the sample papers of neet .
https://medicine.careers360.com/articles/neet-sample-paper
Good luck
Hope it helps