If a guest has switched their sessions but is getting rejected from the session, make sure to look at how the sessions were filtered.
If guests were added to sessions via .XLSX, they should be able to freely switch between those sessions.
If sessions were filtered via custom questions, the guest's answer to the custom question must match in order to enter that session.
If sessions were filtered via registration types, the guest's registration type must match.
To learn how to set filters, refer to the filters section.