If you see this error when using a Personal or Team Page, the Shareable URL section has not been set up for that specific Appointment type.
Navigate to: Appointment Type > open specific Appointment Type > Shareable URLs.
Select either "Allow clients to schedule this Appointment Type via shareable URL, and create a new service ticket." or "Allow clients to schedule this Appointment Type, but do not create a ticket." radio buttons in the Shareable URLs section.
Proceed with setting up the rest of this section to meet your needs.
For more information: