I checked the files. For me, ARCHICAD does not give any such error message as it does to you. So using the File>Interoperability>Merge command I can place the SketchUp file normally, and its 2D and 3D both appear correctly (it is a big textured globe in a wooden frame).
On the other hand, when I try to drag and drop the SKP file into the ARCHICAD Project, it acts like it wants to place it but when I click nothing is placed. However, when I then go to the Object Tool and look in the Embedded Library, the generated Globe GSM file is there, I can select it and place it manually. So in this case there problem is with the placement, not the import itself.
I am doing this on the latest hotfix of AC20. I wonder which hotfix you are using, could that be the reason why the Merge works for me but doesn't work for you.
FYI, I also tried this is AC21 and in that version both the merge and the drag-and-drop placement work as expected.
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