Hii there,

Dear if you have filled your details properly and uploaded your signature in required format then there must be soem network issues or fault from their side. I suggest you to open your portal and login from different browsers, or clear up all the cache memory.

If still the problem persists, please contact the JEE advanced website or mail them As soon as possible. The link is

https://jeeadv.ac.in/faqs.php

You can ask your doubt in faq section. I hope it helps.

All the best!!