It exploited a catastrophic flaw in software design: the assumption that the registry is sacred. The tool did not generate new keys; it simply erased the memory of the failed check. If a game thought you were a pirate because of a typo, CDKeyFixer was the amnesiac drug that made the game forget its own suspicion.

Turn real-time protection back on and add the game’s installation folder as an exclusion to avoid future false positives.

It only cleans the path so your legitimate key can be accepted.

This means the tool cannot find the expected registry path. The game you are trying to fix is either not installed (you need a failed installation first) or the publisher is not supported.