I am trying to change the CSS for the main menu

I am trying to change the CSS for the main menu in the Spirit theme.
Here is what I am doing in Upfront:
Select the option to modify the menu
Select CSS Styles & Anchor Settings
Select the Pencil icon under Element CSS Styles
This launches the CSS Editor
When I edit any of the CSS in the editor and click Save, nothing happens

I have tried this using the Panino theme, and it works properly.