You now have an unactivated Windows 10 that never expires.
Or from Command Prompt (Admin):
Microsoft publishes generic keys that only allow installation , not activation. They get you past the key screen but do not activate the OS.
These keys your PC. They are only for installation.
slmgr /ipk YOUR-NEW-KEY-HERE slmgr /ato
If you’ve previously had an activated version of Windows 10 on your computer, you likely don't need a key at all. Microsoft uses a "Digital License" linked to your hardware.
: If you previously linked your Windows license to your Microsoft account, signing in with that same account after a reinstall or hardware change can restore activation. You can use the Activation Troubleshooter (Settings > Update & Security > Activation) to help with this.