I applied the American English language pack https://translations.atlassian.com/dashboard/download?lang=en_US (the 4.0.4 version, to match our install), changed the default site language, and it doesn't seem to be working. For example, the word "Favourite" is still being spelled in the UK way in the page view. When I look in the preview for the Favourites macro in the macro browser, it correctly shows "favorite", but every other time the word shows it is the other way.
I understand this pack is only 96% complete, but I unpacked the jar and looked in the appropriate file, and it does show the correction. I've also cleared my cookies (in case there was an old setting saved), checked my browser setting (set to US English), and re-logged in.
Any clue why this wouldn't be working?