This error message appears because the Ignore Data Entry Restriction access privilege is not enabled on the System Users screen. To enable the Ignore Data Entry Restriction access privilege, follow the steps below.
Click CoreTime, then click System Param.
Click System Users, then search for the relevant user.
Click Access Privileges, then tick the Ignore Data Entry Restriction check box.
Click Save.
📌 Note: If the above fix is not working, make sure to check if on the Access Privileges page, the Limit Absence Detail Start Date is enabled on the user's system user account ( the one who is adding the absence ), as this won't allow the employee to add the absences.