In order to invite participants to schedule a time on your calendar, it has to be active. After you've finished scheduling participants on a specific calendar we recommend that you deactivate it (though this is not required).
How to activate or deactivate your calendar:
- Click the project name to view the project overview
- Click the "Calendars" tab
- Click status to either activate or deactivate calendar.
When the green "Active" option is showing your calendar is active.
You can also activate or deactivate your calendar when editing it by clicking the "Your calendar is" option in the top right corner: