When prospects attempt to book a meeting from a user's public calendar URL and are seeing the "No times are available. Please contact the organizer" error.
If a user's calendar is currently all booked, users can increase their availability and/or reduce the meeting buffers in the Calendar Settings to see additional times available on their schedule for prospects to book.
If a user's calendar is not booked, the user will need to ensure that any "all-day" meetings are set to "free" within their calendar. If an "all-day" meeting is set to "busy" this will prevent prospects from scheduling meetings on that day, unless permitted to double book meetings.
As the error states, it indicates that no times are currently available on the user's calendar; often times this is due to having a booked schedule.