The latest release of Property Inspection Manager (v4+) is only compatible with iOS 11 or greater, however, if you already have installed PIM an older device you can still update to v3.6.9 which was the last PIM release compatible with iOS 9.3. If you haven't already done so, make sure you upgrade to the latest iOS by simply following these instructions from Apple Support. (Please ensure a backup of your device, which includes Property Inspection Manager, is also performed at this time). 

To update to the latest version of Property Inspection Manager, just open the App Store on your device and tap Updates