Understanding the SketchUp Pro 2020 Classic License and its interaction with the 2021 update

If the license is valid and hasn't exceeded its activation limit (usually two computers), the software will authorize immediately. Finding Your Lost License

The license key and authorization number for SketchUp Pro 2020 are typically provided by Trimble, the developer of SketchUp, through an authorized reseller or the official website. The license key is usually a 20-character code, while the authorization number is a unique identifier that is used to activate the software.