Reset from Windows 10 to Windows 7 after 30 days

I want to reset from Windows 10 to Windows 7. It's more than 30 days since I installed . I have the product key , but when I typed it for download, I got up this message: " The product key you entered appears to be for software that was preinstalled by the device manufacturer . Contact your device manufacturer for recovery options for software. "Can´t I get back the original windows 7 prof.? Are there still a solution for me to get back to win7?

You can download the Win 7 ISO using the Heidoc ISO Downloader available here:
https://www.heidoc.net/joomla/techno...-download-tool

You would need to use the OEM COA Product Key on the COA Sticker for a Clean Install.
The Key used for factory installs is a generic OEM SLP key that auto activates with manufacturer recovery media.
The OEM SLP key can not be used for a clean install.

Here is a tutorial with a picture of a COA Sticker:
Clean Reinstall - Factory OEM Windows 7

You should learn to use backup images before making changes like this.
I use Macrium Reflect free, it has reliably recovered many times, no matter what i did

I've read somewhere in the sevenforums that you can go back to Win 7 if you still have the windows 7 folder. If you have a OEM computer, another way is to do a factory recover (if you still have the factory recover partition). You can start it from inside Windows or during BIOS POST