I installed SketchUp 2019 trial and now I can not see the icon previews in the Windows 10 folders. I tried to uninstall SketchUp 2019, reinstall SketchUp 2018, to associate SketchUp distinction with SketchUp 2018 and put SketchUp 2018 back in the favorite list
Have you tried other (folder) view options? Do you see the same generic icon for every view option?
before the installation of SketchUp 2019 I saw perfectly the previews on the icons Now I see nothing more
When you installed SU 2019, did you right-click on the installer and select Run as administrator?
Seems to be more of a windows thing, my previews come and go. I have not a clue as to what is happening.
For me I had the icon preview working with SU 2018 and then when installed SU 2017 it stop working.
Then when I installed SU 2019 it worked fine.