Holiday time auto population is an automatic process and does not require any manual intervention as long as the holiday calendar is updated and holiday calendar assigned to all users. Holiday hours are added every time a blank timesheet is generated by the system for the user. If you have updated your holiday calendar late, then any such blank timesheets generated in the future must be deleted and regenerated for the holiday hours to be populated again.
If you need further clarification feel free to contact our support team.