However, During a free weekend, you can download and play the full game for 48-72 hours. That is the only safe, legal "free key."
Even if you find a working key, it will likely be deactivated within a week when TaleWorlds detects the same key being used by 50 different Steam accounts. Then you lose your save games and multiplayer progress.
. If you are experiencing activation issues with a legitimate copy, there are safer ways to retrieve or fix your serial key. Risks of Key Generators Malware & Viruses