Error 4780 arises when a staff member has no Weeks per Year recorded on their staff contract. This is not required if they are paid on a daily rate. Click on the error to take you to the staff contract, then click on the cog next to their contract to open up the details.
Working Weeks per Year are entered to the right of the contract. The figure to enter here will be the number of weeks the member of staff is paid, including any paid holiday. Once the data is entered, click on Update to save the information on the contract, then return to recalculate your Workforce Census.