Sketchup to Navisworks issue

[Chumley]

I have imported a 3D MXRoad civils design into SketchUp, tidied it up a bit and re-imported back to AutoCAD for a transfer to AutoDESK Navisworks as an .NWC file for clash detection by the design team.

My client is saying that the faces aren't showing up in Navisworks even though the faces appear in both SketchUp and the 3D AutoCAD design.

Anyone else had this issue?

Thanks.