Unable to measure flatness CZ

[[Re...]]

Good morning,

I have problems with measuring flatness CZ for two planes. 

I created two separate planes, and used fitting elements.

When I select both of the planes and go to Quick GD&T im unable to select the CZ option.

How is this possible and how can I resolve it?

[[Ma...]]

Select both planes and add them into element group. This group can be evaluated as CZ

[[Re...]]

Thanks!