Hi,
the product key gets tied to the system hardware these days.
That means that as soon as you install the right edition of Windows on the hardware that was once activated, it will automatically activate Windows again.
If you had Windows 10 Pro installed, and you install Windows 10 Pro again, Windows will automatically reactivate.
However, without more information I won't be able to help you much more. What do you need the Key for? Did you reinstall, or is Windows deactivated?
Do the other problems still exist?
Regards,
LightJack