mobile
What to do when location isn't working in Trailmap — either in the native app installed from the app store, or on the Trailmap website opened in a browser (that is, the web version of the app)? Almost always the reason is that you've accidentally denied permission to use location, either for the app or for the browser and website. To protect your privacy, your phone (or computer) always asks permission before using your location, and if you answer no, location won't work.
For the native app, the easiest way to get location working again is to delete the app and reinstall it. Then just be more careful about granting the location permission! If you know your way around, you can also change the app's permissions (for location) in the settings, but that means digging deep into the settings menus.
For the web version, the problem can be with the browser's permissions, the Trailmap website's permissions, or both. Test the browser first: open "https://maps.google.com" — note, don't let your phone open the app if it offers to, open the website specifically. Then see whether location works on the Google Maps page. If it does, the browser is fine. If it doesn't, use your phone's settings to grant the browser permission to use location. The Trailmap website needs to be granted location permission separately: the best instructions for this are on Google's pages at https://support.google.com/websearch/answer/179386. Unfortunately the instructions take a bit of technical know-how, because what you need to do varies depending on your phone and browser. Finally, it's best to close the browser completely, or even restart your phone, to make sure the changed settings take effect.