Hello Soumitra, Greetings!

The main reason you are unable to submit the basic registration form can be that the deadline for basic registration will be over. If not, then probably there might be some issue with the website or the registration process. There will be contact numbers or email id's available on the AIIMS website for technical assistance. Kindly contact them and report your problem.

Hope this answer helps you.

Feel free to ask any more queries that trouble you.