This error is caused by an issue with the staff FTE hours in their contract. It may be that the full time hours are lower than the hours per week or that one or both have been entered as 0.0.
Click on the error text or go to Admin > Personnel > Staff and locate the staff member to open their profile.
Click the cog next to their contract name and check their FTE hours against their Hours per week -
FTE = The hours which a full time employee in this post or role would work. For teachers, the standard contractual week is 32.5 hours.
Hours per week = The number of hours worked in a normal week is required for each role or for each post, for staff whether full-time or part-time.
Note: If the staff member has more than one contract, ensure you check all as it may be linked to an expired contract.