Hello Aspirant, hope you are doing good.

So, the registration for the examination in January 2021 was expected to be started by the end of September, and as it is already delayed, you can expect it to be out by the mid of October.  You can go through this article for details about it:

https://news.careers360.com/expect-slight-delay-in-jee-main-2021-january-exam-dates-prof-ramgopal-rao-director-iitd

Till then, don't worry about it, and keep checking the official site every now and then, so that you get to know about any new information.

Hope this helps you. Good Luck!