There are two ways to solve this warning:

1. If you go to the schedules tab, you will see that your model has at least one of three schedules types: air velocity, clothing insulation and/or work efficiency. If you click on one of these schedules you can tell it's not just the name but also the type if the schedule type specifies it as so.

_2. If you go to the loads tab and select one of the people definitions, you will notice that there is some text: Add/Remove Extensible Groups with a small plus and a small minus icon to the right. If you click on the plus icon you add the ability to select a comfort model to be analyzed for that people load to be utilized somehow in the reporting.