For specific troubleshooting, historical versions are often referenced on the SketchUcation Community forums :
Installing an old version of LibFredo6 follows a slightly different path depending on your SketchUp version: LibFredo6 - SketchUp Extension Warehouse Libfredo6 Old Version
If you are running SketchUp 2016, 2015, or older, installing the current version of LibFredo6 from the SketchUcation Plugin Store will likely result in error messages at startup. These errors occur because the new library code relies on Ruby functionality not present in older SketchUp versions. For specific troubleshooting