Hello Bertrand,
it's not an error int he IP geolocation. Probably this happens because your PHP settings don't allow the use of file_get_contents function related to the PHP setting for "allow_url_fopen" that must be "on".
Indeed the IP geolocation is done using
http://www.geoplugin.net/ opening a connection, if not possible the component fallbacks on the browser language header. This explains your result.
If you have issue with this contact your hosting provider in order to change PHP/Server settings to be able to connect to
http://www.geoplugin.net/
As an alternative you can try to switch to the PHP Curl library using the JRealtime configuration as visible in the image below:
Best regards
John