Model imported from SketchUp disappear

Hi. I just discovered that the main structure of my stage (Floor, ceiling, roof, walls) suddenly disappeared from Augmented3d. However, many other things, also from SketchUp are still visible, as also all the fixtures. I can see it in the list of objects, but when i hover over it is says "0 triangles" .All the other objects have between 70 and 1000 triangles. It was working fine before. What has happened? Im reluctant about doing the whole thing again without knowing what caused it.

Any suggestions?

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