When adding a working time to your Calendar, there needs to be at least 1 hour available to be able to save that slot. This is because all sessions are booked into 1-hour slots (50-minute session plus a 10-minute break between clients). 

If you are receiving an error message stating that a working time will not result in any available slots being offered (screenshot below) this is usually due to the start times entered, or due to the working time being less than 1-hour long.  

To resolve this, first check that the working time covers at least 1 hour (ie. 3pm - 4pm instead of 3pm to 3.50pm).

If the working time entered covers at least 1 hour, please ensure the Session Start Times entered at the bottom of the pop-up match the availability you are trying to add.

For example, to add a working time for 5.30pm - 6.30pm, the Session Start Times also need to be set to 30 minutes past the hour as per the screenshot below :