You may check the location service and WiFi setting on your phone. It's important that both GPS and Wifi(even if they are not connected) are activated on your phone.
Please note that accuracy depends on many factors, such as your environment and your phone. There is moments when the highest accuracy will not be available(underground for example)
Please refer the below instruction for the detail.
1. Check the location Settings
- Settings > Privacy > Location Services > iSharing > "Always"
2. Turn on Wi-Fi
iSharing uses Wi-Fi signal to estimate a current location when GPS signal is not available(indoor or underground). We recommend you to turn on Wi-Fi even if you don’t use it.
- Settings > Wi-Fi on
3. Make sure Internet connection is active
Since iSharing updates your location via 3G/LTE/WiFi, your iPhone always should be connected to the internet.
4. Do not remove the app from background
iSharing need to keep communicate with an iPhone even if it is under background. Don't worry about the battery consumption. iSharing consumes just 1% of battery life over 24 hours.