Problems with the thickness of shells

Good morning,

I´m new here and try to simulate a mixed model with shells and solid parts. In the shell manager are all sheets listet which are going to mesh as shell.

Unfortunetly there is un error when  I try to mesh the whole assembly: The thickness for one or more shells are not defined!

How can I find the shell which is not correctly definded?

Thank you

SolidworksSimulation