Hi Nicola
I have been reviewing and testing this before escalating to the developers (which I've now done).
I recreated a clean online test site, you can see the test page here: hidden link
We each tested with a variety of browsers and found that the "Use my location" button worked in all, except FF on Windows only.
On Chrome and Edge, permission is requested as soon as you load the page. In Firefox and Safari it is only requested when you click the "Use my location" button.
In each case clicking the "Use my location" button populated the relevant input with geo-coordinates of the user.
If they then press Submit the filter works as expected, only results within the specified distance are returned.
The problem occurs when trying to output the distance of the found posts from the user location.
This is done with the toolset-maps-distance-value shortcode, and when inserting this shortcode it specifies that it is necessary to wrap the shortcode inside the wpv-geolocation shortcode.
The loop output of the View on that test site looks like this:
<wpv-loop>
[wpv-map-marker map_id='map-1' marker_id='marker-[wpv-post-id]' marker_field='wpcf-location'][/wpv-map-marker]
<h3>[wpv-post-link]</h3>
[wpv-geolocation][toolset-maps-distance-value origin_source='visitor_location' postmeta='wpcf-location' unit='mi'][/wpv-geolocation]
</wpv-loop>
Only in Chrome and Edge does this work, and display the calculated distance. In FF and Safari it continues to display "Your location is needed to show this content" where the distance is expected.
That's what I've escalated to the developers.
This is a problematic area, as browsers prioritise privacy and security. The settings for these may vary between users, and different users may also load privacy-related extensions that can impact this.