If you have a registrant who was invited from the waitlist or invitation only event doesn’t register in time, they will move to the “Declined, Removed, or Expired” section.
If you wish to change your registration from “Waitlist / Invite Only” to a normal registration type (i.e. Unlimited, Limited), you will need to clear everyone from your wait list or invitation list first including the "Declined, Removed, or Expired" section.
Go to your Waitlist or Invitation page to see any pending invitations that have been sent or expired.
Check the "Declined, Removed, or Expired" section below and remove any registrants as shown below.
Once you have done so, you can go and Edit your event and switch your registration type.