Hello,

We all know due to pandemic situation JEE Mains last two sessions which are April and May 2021 was postponed. Already two sessions are over and there correction windows also closed. So April and May session date is not declare till now. May be they will declare soon. If you want to register yourself in those sessions so there will be sure present the correction window. But now registation form is not open and that's why no correction window present. You have to wait for the notice from NTA.

All the best.