There are two reasons why a time won't show up when scheduling an appointment.
1) Your availability isn't set up.
By hovering over 'Calendar' you will see Availability. If you have zeroes across all times, this means your availability is not set up. Clicking the arrows on this screen will allow you to fill these time slots in
2) You selected the time option before choosing a valid date.
If you attempt to schedule a time before choosing a date, you will see no options. For example, if you choose yesterday's date, you will have no time options, because that day is in the past. If you choose tomorrow, and then choose a time, you should see time selections if your availability is set up.
Please let us know if this information did not help. Screenshots of what you're experiencing would also be very helpful in investigating your individual issue. Once you have the appropriate information, please do not hesitate to reach out to Club OS Support at email@example.com and we will be happy to assist.