Assuming SKAction.playSounfFileNamed is just a typo, your (pseudo?) code should work, I think, which points to your sound file itself. Check naming and try something else to confirm. Be sure to option-clean the build folder if you juggle assets/names.
Your first example is correct. Build it, install it on your device. Quit the app. Unplug your device. Launch the app again. See if it works.
Sometimes sounds get muted when the device is plugged in while testing.