I have a problem with my thumbnail on windows explorer. I’ve been already uninstalled another sketchup except my sketchup 2017. although i’ve been reinstalled my sketchup 2017 64 bit. but the thumbnail is only view a sketchup logo. not my model.
One way to see the icon as the view when last saved is to use XnView. I have not used in years (I am using MooTools 3D browser now), but it used to work just fine for this purpose.