There currently isn’t registration availability until 2022... not sure then calendar had no availability for years??!?! Anyway people can register sooner?

You can't register until 72 hours before the time and date of the event so if it's on Monday at 9 a.m. the registration would open the Friday before at 9 a.m.

Like Jeff London says, keep checking availability on their webpage exactly 72 hours before the registration day. Perhaps you want to try right after midnight before the registration date, this is, if the registration day is on a Monday, try the Friday before right on the first second of that day (00:00:01 of Friday). Good luck!