Here’s another workaround that the knowledge team is testing.
- Rename your existing “/Applications/SketchUp 2016” folder to something else.
- Create a new “/Applications/SketchUp 2016” folder
- If you don’t already have a copy of the 2016 SketchUp installer, download one.
- Double-click on the installer.
- In the window that opens, double-click on the “SketchUp 2016” folder in the installer.
- Copy the three applications to your desktop (SketchUp, LayOut, Style Builder)
- Run each of them once from the desktop.
- Copy the app bundles to the folder you created in step 2
This series of steps will trigger Sierra to clear the quarantine flag.