Models converted using 3DXChange 2.0 should open without problems in iClone 4.
If you want to import any models from SketchUp then you need to make sure that they are saved as .skp for SketchUp 6. You can do this by selecting "Save As", then in the drop down file type window select SketchUp version 6.
Gerry
System: Win 10 Pro (21H2), Asus X99-E WS, CPU i7-5930K -3,5 GHz, 32 GB DDR4 2666-16 RAM, NVidia GTX 1080 Ti GPU - 11 GB VRAM(Driver Studio-536.99), Samsung 850 Pro 512 GB SSD, 6 TB HD storage.