arpsa said

I have added a Finnish language pack and schwitched it on, but it doesn,t work. Firefox 59.0.1

Maybe you'd like to download the latest Firefox version in your language, instead of using a language pack :

https://www.mozilla.org/en-US/firefox/all/?q=Finnish

How did you try to switch on the language pack?

You can possibly use the command line switch to select the locale.

• https://developer.mozilla.org/Command_Line_Options

Note that general.useragent.locale no longer works in Firefox 59+. You need to use intl.locale.requested