This occurs when a CDP file is corrupted or belongs to a newer version of Trainz than the one you are running. You must open the archive using an external unpacker or update your game.
The safest and most reliable CDP converter is already built into your Trainz installation. The utility features native tools to handle these archives. trainz cdp converter
Trainz will extract the CDP archive into a standard file folder located in your local app data directory ( editing folder). Step 3: Access the Extracted Files This occurs when a CDP file is corrupted