Free upgrades to Windows 10 from Windows 7 and 8 were supposed to have ended in July of 2016. However, Microsoft didn’t really enforce that and users were still able to use their product keys from Windows 7 and 8 to activate the upgrade to 11.
However, on September 20, the company but out a brief announcement on a site aimed at their retail partners who install Windows on devices saying that those activation keys would no longer work:
“Microsoft’s free upgrade offer for Windows 10 / 11 ended July 29, 2016. The installation path to obtain the Windows 7 / 8 free upgrade is also removed. Upgrades to Windows 11 from Windows 10 are still free.”
So, if you’ve already upgraded to Windows 10, you can upgrade to 11 at any time, assuming your PC can handle the transition.
If you haven’t upgraded your older devices, that ship has sailed. If you are using Windows 7 or 8.1, you should stay the heck offline, as they are not protected from viruses or malware. It may be time to upgrade to a new PC for security’s sake.