After some of my earlier suggestions I found that a more sure way to fix the problem was to go into Default Apps, choose Choose default apps by file type, then scroll how to .skp or .layout in the list. In the apps that you will see that can open that file type, choose the upper one. It may be a duplicate of SketchUp 2019 or earlier, but really it is SketchUp 2020.
Test to see if you picked the right one in the list by double clicking on a SketchUp file.