Upfront editor CSS editing error

In more of my attempt to use the spirit theme and make it a version of my own. I was working on customizing the main navigation bar.

I click on the navigation and choose the settings option.
I then choose to open the "Element & CSS Styles option" at the bottom of the window and then choose the pencil (edit style) option.
It then opens the css elements and code section at the bottom of the page for "navigation element" for style name - "main-nav".

It is my want and intent at this point to take the current "hover" color option
from,

ul.menu li:hover a, ul.menu li.current-menu-item a, ul.menu li.current-menu-ancestor a {
background: #4f7e7d;

and change it to,
ul.menu li:hover a, ul.menu li.current-menu-item a, ul.menu li.current-menu-ancestor a {
background: #2B2B2B;

Which seems simple enough. Unfortunately when I hit the "save" button, nothing happens.
Up until this point I haven't had any issues with saving changes or undoing changes made. It almost seems like the "save" button just doesn't know what to do when its pressed.

Am I missing a step? or is there somewhere else that i am supposed to make these changes from?

Thank you in advance for continuing to answer all my questions.