The steps provided are only applicable if you still have the device. If it is lost or stolen, then there’s a tendency that the device has been turned off and location services are not accessible anymore. You will need to lock the device to prevent unauthorized access to the phone’s files and other sensitive information.  You may also need to check Apple's system status as there are cases where the issue is coming from their server. Simply visit the official Apple System Status site and look for Find My. If you see a green dot next to it, that means it is working fine. A red or yellow dot will appear to indicate that the app is not working and the reason why location services aren’t functioning properly as well.  Just in case that you have your phone but the issue persists after performing the given steps on this article, consult the nearest Apple service center for some possible recommendations that can be done on their end. It might be an issue that needs to be checked by their team.