One of the main reasons why a browser can detect your location is a browser popup that asks you to share your location with a specific website. Once you click "Allow", unfortunately, the browser extension cannot hide the location anymore because it is out of proxy scope.
To change location permission, you can click on the lock sign again and, under the "Location" section, choose to disable it.
You may also check out our blog post that gives tips on how to change location-sharing services when using the Chrome browser.