SketchUp Pro "Classic" licenses are no longer available for purchase. As of November 2020, Trimble transitioned entirely to a subscription-based model. How to Manage a Classic License
Some key points to keep in mind:
Device Limits: A single-user Classic license can be installed on up to two devices, but only one can run the software at a time. Current Options sketchup pro classic license key
If you already own a perpetual license and need to activate it on a new device, follow these steps provided by SketchUp Help Open SketchUp SketchUp Pro "Classic" licenses are no longer available