Your profile says you are using SketchUp 2015. If that is correct, the 3D Warehouse hasn’t supported that version for several years. You can go to the 3D Warehouse through your internet browser with this link: https://3dwarehouse.sketchup.com/ but keep in mind that most of the content will only be available for SU2017 and above. (Maybe some 2016) You can download the Collada file, though, and import the .dae file into SketchUp 2015.