Finished this afternoon - want to re-play the heist but I can't because it won't let me.
If you want to replay Mission 1, close the app, open a Finder window, go to your user folder > Library > Preferences and delete com.macheist.MH4-Mission-1-Mac.plist and its lockfile.
The nanoMissions are done differently. To replay those, close the app, open a Finder window, go to your user folder > Library > Containers, and delete the "com.Macheist.MH4-NanoMission-#-Mac" folders where # is the number of the nanoMission you wish to replay (so far, 1 or 2).
If the Library folder isn't visible in your user folder, open a terminal window and type "chflags nohidden ~/Library/" (no quotes). Type in your account password, and it will show up.