Hello Vimal,

Check whether the site to which you are entering your Hall Ticket number is authentic and authorized.

Log out from any other devices which you use regularly.

Try logging in with some other devices.

If nothing helps, try contacting the site administrator with the help of the number provided in the site itself.  They ought to have some ways to resolve your issues.

Precautions:

Always take a photocopy of the entire Hall-ticket as soon as you receive it, because it's better than writing up the number in a piece of paper.

Periodically check your account by entering the details to the site to avoid last minute hurdles.