For me also, it is showing that either application no. is incorrect or wrong date of birth or admit card not available. For my friend also , it is showing same

Hello Shraddha!

I hope you are trying to download it from the official website and putting in all the details correctly on the link given below-

http://bhu2.ucanapply.com/AdmitCard2018/entrance/?app-id=UElZMDAwMDAyMA==#

If you are still unable to download it, you can contact the Controller of Examination, BHU via phone or e-mail. The contact details of the same can be accessed from the link below -

http://www.bhu.ac.in/admin/ce.php

Good Luck!