Can you select all entities (CtrlA) and look at the number of entities in Entity Info. Is it before and after import the same or different?
If it is the same, the component failed to import for some reason (this would normally show an error).
For example, something like this can happen when you have a SketchUp version that is not compatible (anymore) with 3D Warehouse, like 2016 (see announcement). But in your profile, you write that you use SketchUp 2020. Is that correct?
Workaround:
Open 3D Warehouse in a web browser, navigate to the desired model and download it (when using an older version of SketchUp, check the compatible .skp version or choose .dae). In SketchUp, import the file with File → Import… → 3D model.