If general troubleshooting didn't help, try these steps:
Make sure that you're signing in with the Apple ID that you use with iCloud. When your device has been set up to use a passcode, you're asked to sign in only the first time you open Find My iPhone. To set a passcode, go to Settings > General > Passcode Lock (or Passcode & Fingerprint), then tap Turn Passcode On.
This message appears if no device is set up with your iCloud account and Find My iPhone is turned on. If you still have the device in your possession, go to Settings > iCloudand make sure that Find My iPhone is turned on.
This message means that Location Services was turned off on your device while you were using Find My iPhone to locate it. Find My iPhone won't be able to locate your device, but you can still use the app to take certain actions:
Make the device play a sound
Display a message on the device's screen
Lock the device (using the Lock feature in iOS 5.1.1 or earlier, or Lost Mode in iOS 6 or later)
Erase the device.
Note: The ability to use Find My iPhone to locate your device on a map is not available in all countries. Locating your device on a map requires Maps data to be available in that area. All other Find My iPhone features will still work.