Game runs slowly, lost sound, or shows any other unexpected behavior.
1) The first thing to try is turning your device off and back on again.
2) Then, make sure you have the latest iOS update for your device.
3) You can also try deleting and re-downloading the game from the App Store. You will not be charged again for downloading the game, and you should not lose any of your game progress.
Finally, if your device is modified or jailbroken you may want to try restoring it to default factory firmware.
ADDITIONAL TROUBLESHOOTING FOR "LOST SOUND"
1) Make sure your physical mute switch is not on. Try toggling the mute switch off and on to make sure.
2) Open Zombie Gunship, and on the Main Menu, tap the gear icon in the upper right hand corner, from there toggle Audio off and on. After, you may reboot your device by completely turning it off and back on again.
3) On iPad in the General Settings you can set the switch to be lock rotation or mute. We have reports that toggling between those settings fixes the missing sound problems.