DLL files rely on core Windows architectures to run properly. If your system's runtime libraries are outdated or corrupted, Mortal Kombat X won't be able to read the Steam API.
“The program can’t start because steam-api64r.dll is missing from your computer.” steam-api64r.dll missing mortal kombat x
Short example error message to display: "Error: steam-api64r.dll not found. Verify game files in Steam or reinstall the game. Check your antivirus if the file was quarantined." DLL files rely on core Windows architectures to run properly