Zhann, "1) make sure you're in full view in the preview window, that becomes your thum, some imported meshes do not show for some reason...." yes, by "Full view" do you mean "Close up" or "Normal"? And then what? How do you get what you see in the preview window to be what you see in the thumbnail?

Measure your mind's height
by the shade it casts.
Robert Browning (Paracelsus)

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