Sites generally guess your location based on your current IP address, assigned by your service provider (or VPN service, if you are using one).

Sites can request more specific information, and many do. In that case, Firefox will prompt you for permission and display an icon toward the left end of the address bar. If a site is not requesting information, perhaps it doesn't have that feature, or you need to go into the page with account settings or other customization.

Is there a particular site where you have this problem? Note: when sharing a URL, please put a space before the .com or .org in the address to break the link. That will avoid a delay caused by the forum's spam moderation feature.

What do these websites say about your location?

http://whatismyipaddress.com/ Under the map, look for Location Not Accurate?

http://browserleaks.com/geo

https://whatismyipaddress.com/geolocation

https://html5demos.com/geo/

https://www.iplocation.net/find-ip-address

How to set your location manually in Firefox(Windows) https://support.mozilla.org/en-US/questions/1197142#answer-1115502