Your CPU does not support specific instructions (SSE 4.2 / AVX) OR you are using an old 3DM crack on a modern Intel/AMD processor.
— Good luck, Boss.
The "Crack Fix v3, v4, v5" rabbit hole got dark fast. Because MGSV was so hyped, scammers flooded the market. The actual 3DM crack was stable eventually, but the "Fixes" circulating on random forums were often just keyloggers wrapped in a steam_api64.dll . Metal Gear Solid 5 Phantom Pain Crack Fix