Modern software like Driver Doc uses online activation servers. The moment you enter a key found on a public forum (like Reddit, GitHub, or random blogs), the software phones home. If that key has been used more than 3 times (or is a known leaked key), the server blocks it. You will see an error like: "Invalid licence" or "Key revoked."
: Paste the key (CTRL+V) into the text box and click "Activate Now". Free and Safe Alternatives licence key for driver doc free