Location Services stopped working on kid's iPhone

I manage my 16-year-old son’s phone through Apple Family, and have always been able to see his location. But a few weeks ago, his phone suddenly stopped sharing his location, and we can’t figure out how to turn it back on again. When my son tries to share the location, the message “no active location” appears. In his settings, both his “iCloud” and “Find My” are grayed out. Since he just got his driver's license, I need to know his location!

[Re-Titled by Moderator]