For Sony Xperia mobile phones error 191 is strictly related to the compatibility factor. When you encounter this error, it means that the phone is not compatible with the application. In this case, you can either look on Google for the APK file (not recommended!!!) or upgrade to a newer and more powerful phone. However, go to Settings > Applications manager > All > Google Play Services & Play Store. Tap on each one and clear the data and cache, reboot the phone and let it for a few minutes then try to download it again.