I would suggest having one of the other phones next to you to troubleshoot. While it may seem that the error is on your side, in most cases the Location Not Found message is due to something on the other phone. It may be as simple as restarting the device or toggling the Share My Location off/on using the other device. Verify that iOS is up to date on the other devices. The other device will need to have internet connectivity, so if there is no cell connection, then they would need to be connected to WiFi.
For most users on this forum, toggling the Share My Location and Location Services switch on the other device followed by a restart solved the problem.