--NOTE-- This issue is resolved in Version 12. Get the latest version HERE.
When attempting to run the Scheduler in Gradience Attendance and [Holidays] is deselected, the error shown below appears:
To work-around this:
1. Click Reports > Scheduler Report.
2. Set the desired data range and filter settings.
3. [Manually] select every Code that you want to be reported [except for] Holidays.
4. Click Preview and then print the report if necessary.
5. We apologize for the inconvenience.