The SketchUp "Classic License" refers to the older, perpetual licensing model that Trimble officially retired in November 2020. While these licenses are no longer available for purchase, they still function for the specific versions they were originally issued for (e.g., SketchUp Pro 2020 or earlier). How to Use Your Classic License Key
Since you can no longer obtain a classic key, here are the current paths: Getting Started with SketchUp FREE in 2025 Part 1! sketchup pro classic license key