Hello,
Does the .iso file contain the extension .ecm by any chance, after the .iso?
If this is the case, you need to downlaod the ECM tool, which will contain an .exe file named 'unecm'.
If you drag the .iso file into that tool, it will undergo a 'decoding' process, in which a new rom will be
formed and will no longer have the extension .ecm, therefore making it playable.