You will encounter this error when the employee's calendar has not been initialised. Please check as follows:
Ensure the calendar ID that has been assigned to the employee.
In the Core module, click Employment Details, click the Miscellaneous tab.
Check the Calendar ID.
Initialise the calendar
Click Setup and select Initialise New Year Setup.
Click Step 1: Initialise Calendar.
Select the Calendar ID that you checked earlier in step 1.
Bring it over and click Confirm.
Initialise the payroll
Go to the Payroll module, click Pay Record, and click New.
Check the month and click Next.
Select the staff and click Confirm.