Serial keys are unique. If a key is already registered to another user, you will be blocked from using the Download Station and multiplayer servers.
This is the most reliable method. Log in to the Trainz portal . Navigate to "Serial Number" or "My Digital Downloads." If you bought the game digitally or registered your physical copy previously, the key will be listed there. CD KEY trainz simulator 12 46957 serial
Build 46957 has specific update requirements. Using an invalid or "blacklisted" key often prevents the game from patching correctly, leading to crashes and "Internal Error" messages. Troubleshooting Build 46957 Activation Serial keys are unique