The Mac computer (actually any computer) needs WiFi enabled and connected in order to determine your current location.
For more information on enabling WiFi, please read our article at:
And here is the technical info:
If you open the Apple Maps app, and try to determine your current location with Apple Maps, you’ll find the same behavior. In other words, no app that uses Apple Maps (as The Ultimate Public Campground Project does) will be able to determine your current location if Apple Maps can’t.
Please wait... it will take a second!