Hiii

Altough you have not mentioned but i believe you are asking about the AIBE XIII. Many candidates were facing this issue, Please ensure that you application is correct and has been accepted, only then you will be able to download the admit card. If everything is correct then you must contact then soon by email or through customer care service and put up your issue in front of the authority so that your problem is solved soon.
Also keep trying to download the admit card in non peak hours.

Thanks!

Hello Applicant,

Please specify the name of the exam for which you want to download the admit card.                                    

It is difficult for us to help you like this with such limited information.