This is a continued discussion from Why Can’t I Install A Plugin on My Sketchup?
Not too many people on this forum do anything with that file extension. This inquiry would be better suited for the Muvizu forum.
I can though guess from the error message that your SU model had a mix of front and back faces on the outside of the model. Faces are sided. The whitish default face is the front face and the bluish face is the back side. The face normal points perpendicularity outward from the front face. Many apps, like renderers and 3d printers, need to know what is inside and outside, and does its work only front faced-mesh parts.
The SU model also may need to be a “water-tight” solid - no holes. You need to check with the Muvizu folks for the exact requirements.