If the above methods do not work, you can try using a DLC unlocker tool. These tools can be found online, but be cautious when downloading and using third-party software.
Instead, do this:
Valve is not stupid. While they rarely ban for single-player DLC unlocking (as it doesn't affect VAC-protected multiplayer), they do perform sporadic banwaves. If you use CreamAPI on a game with Steam Achievements or Workshop integration— Shogun 2 has both—your account can be flagged for "license tampering." A permanent account ban means losing every game you own. Total War Shogun 2 Dlc Unlocker