The Find My iPhone app is a safety tool for tracking your phone. All Apple devices, including iPad, iPod, and Mac, have this feature. If your phone gets lost, stolen, or misplaced, it works amazingly well. But in case. But some the tool doesn't work properly then there are some reasons that tool doesn't work -
1. iPhone is not connected with the cloud services properly.
2. Your iPhone has a weak connectivity
3. Find My iPhone is turned off.
4. an Older version of IOS
5. The iPhone's date and time aren't correct
6. Older hardware or bug-ridden software.

For more read - https://allinsider.net/what-does-live-mean-on-find-my-friends-on-iphone/