If you're trying to add a customer onto a session via the Add attendee button on the Attendees page but are not able to find them, then there's two possible reasons for this:
The customer was previously an attendee on this session but has since cancelled their booking. Simply expand the Cancellations section on this Attendees page and click on the + sign under the Add attendee column next to this customer to rebook them onto this session.
The customer was previously an attendee on this session but has since cancelled their booking and joined the waitlist. Simply expand the Waitlist section on this Attendees page and click on the + sign under the Add column next to this customer to rebook them onto this session.
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