Stress result requires density, poisson's ratio and modulus of elasticity. To create a FOS plot you must also have ultimate and yield stress limits. Check each material properties and make sure all of these fields are filled in. If some are missing in Solidworks materials then you will need to create custom materials.
Custom materials were used, GRP as the skin and Syntactic foam as the core. below the properties as defined:
and the Syntactic Foam:
I am using the composite symetric shell option. The stress calculations seems correct. But for FOS I am getting the following error: "All materials do not have sufficient stress limits to calculate the requested results....'. I would appreciate any additional advice to overcome this problem.