The 3D Warehouse only supports the latest three versions. SketchUp 2018 and earlier are no longer supported. You can get some components by searching the 3D Warehouse in the Components window instead of using the 3D Warehouse UI. Alternatively you can access the 3D Warehouse in your internet browser, download the Collada file and import the .dae file included in that Collada file.
From August 11, 2021:
And from the Help Center:
https://help.sketchup.com/en/current-minus-two-version-policy
This is not a SketchUp bug.