What is shown isn't your actual location, but the location of your ISP, or maybe you're using a proxy.

Go to Advanced/Network/Connection and make sure No Proxy is selected.

Hi mattcamp,

I have the network proxy turned off. As you can see on my screenshot (the right bit), my ISP is located in Coevorden, The Netherlands based on Geo IP. That is about 1050km away from the location reported by Firefox to the JavaScript API. Chrome/Edge report my location correctly, both in by the Geo IP and the JavaScript API.

Does the website use SSL? As of Firefox 55, "Sites that don’t use SSL can no longer access Geolocation APIs to determine a user’s physical location" (see the associated bug). This may also be true for Chrome, but switched off.

Did your geolocation work properly in Firefox when you were in France, and with the same version? That would indicate some cached location is used, which you might be able to pinpoint by quickly creating a new profile.

Tonnes said

Does the website use SSL? As of Firefox 55, "Sites that don’t use SSL can no longer access Geolocation APIs to determine a user’s physical location" (see the associated bug). This may also be true for Chrome, but switched off.

Yes, I tried using it on the site mentioned in the OP.

Did your geolocation work properly in Firefox when you were in France, and with the same version? That would indicate some cached location is used, which you might be able to pinpoint by quickly creating a new profile.

I have never been to that particular location in my live and this is a new laptop, with a new profile (with Sync though). I will try using a new profile, I will edit this message to report back in a bit

I switched profile and now everything is working as it should. Very strange!

Thanks guys!

Thanks for your feedback, glad to see it works now.

One question though: did you use the profile you were using for 56 (and perhaps 55) Beta for 54 release again (at least once) after using it for any of those versions? If so, that may have caused parts of the profile to be corrupt, possibly including geolocation related settings or info. On the other hand, that would rather affect 54 versions after downgrading.

If not, it may just have been a per-website or global permissions issue (geo.enabled?) that you can still get a hold of when your other profile is still accessible, which may prevent you from migrating settings and add-ons. See this question for more on that, as well as the Page Info page / support article.