Planning any effort for a resource results in an overbooking warning/error
Please check
- the resource has enough working days during the planned period
- the resource is not being unassigned during the duration of the assignment
- there is no effort planned for other tasks in other projects or in the calendar
- the resource daily capacity field should be blank (to use the workgroup setting) or a value >0, like e.g. 4 (half day) or 8. Do not put in 0, this will make it impossible to plan any effort for the resource.