The Warehouse only supports the three most recent versions of SketchUp. 2016 is no longer supported. You can access the Warehouse through your Internet browser and download the Collada file which you can then import into SketchUp or you can try Eneroth Open New Version which is available in the Extension Warehouse. Download the SKP file through your browser and run the extension from the file menu in SketchUp.
FWIW, you may still find some 2016 files but the Warehouse is no long converting uploaded files to 2016