Hey everyone - when you import your model into CryEng there are often faces missing from the model (completely, or from specific angles).
To fix this, in Sketchup, go to the Playup toolbar and select "Check Normals". Basically each facade needs to have a thickness of some sort (single planes don't work). Anything displayed in green won't be seen in CryEng. For those that are Green and have a thickness, select the face and right click to "Reverse Faces" (Sketchup treats faces as either interior or exterior (interior faces aren't shown in CryEng).
Hope this helps...