The participants manage to send their confirmation email again.
In accordance with the GDPR, the participant sees their registered information.

End customers, your customer – the participant has their own account where they can log in and where the participant finds all forms (Registration form, interest lists and order form) on which their e-mail address is registered.
They can send out their confirmation email (s) again, see their invoices and receipts from their registrations with their registered e-mail.