Hi Michael, did you possibly upgrade your OS to a new version in the meantime? On Sierra Apple has made some changes to how non digitally signed apps run, now they are read only unless they are running from the /Applications folder. So because of this you have to move MoI to the /Applications folder in order for it to run. But if that's the problem you should usually get a warning message about "Info.plist is read only".

You also might try doing a system reboot and see if that helps anything.

- Michael