You restored your device, updated your iOS, or switched to a new device and your coins and upgrades are missing.
First, make sure you have updated to the latest version of Zombie Gunship available on the App Store. Open Zombie Gunship, and on the Main Menu, tap the gear icon in the upper right hand corner. From there tap “Restore Backup”. If this does not work, please email us at firstname.lastname@example.org, let us know you have lost your upgrades for Zombie Gunship and we will be happy to assist you.