Broken system files can interfere with DLL loading.
Here is where things get interesting. The standard file is steam_api64.dll . The file causing your error is steam-api64r.dll (note the lowercase 'r' at the end, or sometimes separated by a dash). steam-api64r.dll error
No matter the phrasing, the result is the same: the game cannot proceed. Broken system files can interfere with DLL loading