Late registrants will get the emails from the day they register onward, but not any that they've missed but you can manually send to them.
ie. Deadline to enrol is Friday.
Someone enrols Saturday - they will get all of the emails.
Someone enrols Tuesday evening - they will get all of the remaining emails (Wed/Thurs/Friday) ... But you can manually email them day 1 and 2 and excellent excuse to have them hop on a call (which is the whole point of this)
Someone enrols 2 weeks later after challenge is over - they will get none of the emails, but you still get the lead and an excellent opportunity to book a call and what had them register for the challenge and do Call #1.