: Open your Autodesk 2020 software (e.g., AutoCAD, Revit, 3ds Max). : In the "Let's Get Started" window, select Sign-In / Single User Authentication

Autodesk 2020 products, the activation process depends on whether you are using an official license or troubleshooting a legacy installation. Since the 2020 release, Autodesk transitioned toward Sign-In (Autodesk ID) licensing, which does not require a serial number. Official Activation Guide Launch the Product

tool via an elevated command prompt to reset or change license methods. Service Update : Ensure the Autodesk Licensing Service

: Choose "Enter a Serial Number" in the startup menu. The software will generate a Request Code Enter Activation Code

If you encounter "License Not Valid" errors, you may need to reset the licensing service: Licensing Helper AdskLicensingInstHelper.exe