If the attendance is showing absent for few employees on greytHR the reason could be you would have updated the day as Restricted Holidays (Optional Holidays) on your greytHR application.
Revisit the holiday list by navigating to the Holiday List page from the Leave Setup section.
Employees can avail the Restricted Holiday only based on eligibility also employees need to apply to avail a restricted holiday. Else system will mark the day as absent.
Watch the video to know how to add or edit holidays on greytHR.