My app preferences are not updated

The app settings can be changed at any time on the app preferences page. After you change any value, you must click Save (on the header, or at the end of the preferences options) for the new settings to be applied:

At that moment the new settings are applied:

However, please note that the preferences are cached for a minute in your browser so, if you had already opened a page with the app widget in your browser, you may have to refresh the cache in order to see the new settings applied. You can do that easily, for example, by pressing CTRL + F5 if you are using a Windows machine or SHIFT + 'Reload button' if you are using a Mac.

As  a last  resort, you can always clear your browser cache, but this should not be normally necessary.

Please check https://en.wikipedia.org/wiki/Wikipedia:Bypass_your_cache for shortcuts for all browsers and instructions on how to clear caches.