Hi, I'm Bernard. I'm happy to help!
Previously, you were using Windows 11. Is that correct? If yes, and you upgraded from Windows 10 to Windows 11 before, it should be a digital license that is bound to your Microsoft account. To upgrade again, kindly follow the steps below:
First, make sure that the PC is compatible with Windows 11:
Kindly run the PC Health Check: https://aka.ms/GetPCHealthCheckApp
For reference: https://support.microsoft.com/en-US/Windows/Experience/Compatibility/how-to-use-the-pc-health-check-app
If it passes the health check, I suggest doing an in-place upgrade, which will upgrade the device to the latest version and repair all issues without deleting any files.
Go to the Windows 11 website: https://www.microsoft.com/en-us/software-download/windows11
Under Download Windows 11 Disk Image (ISO), select Windows 11 (multi-edition ISO)
1. Once done downloading the ISO, kindly right-click on the ISO, then click Mount>click Setup.exe
2. You may be prompted by User Account Control. Click on Yes if so
3. In the Install Windows 11 dialog, click Next
4. Setup will check your PC and show a license agreement. Click on Accept in the license terms dialog.
5. Wait for the setup program to check for the available free space.
6. On the Ready to install page, make sure Keep personal files and apps has been checked.
7. Then click Install and just follow the prompt.
8. Windows 11 will restart your device several times and lead you to the lock screen. Depending on the options you set, it will keep all your files, apps, and user accounts.