Is the game in a "write-protected" (="read only") folder location on your system, or on a USB-stick?
Have you unpacked the game files from the .zip?
Do you get an error message?
Have you searched for "remove folder protection mac" or something like that? I see several articles when I google this which might help, but I can't tell what fits or works for your situation, that's why you have to check yourself.
Else, you could try to move the entire game folder to a different location. The desktop or similar, or any folder which isn't set to "read-only".