Custom CSS not applying to Posts list

Hello,

I have a rather straightforward site that is not updating my posts element's "custom css" as it should. In Upfront, the CSS functions as it should: in this case, a simple hover effect that shows an opaque background color that permits easier reading over an otherwise image background. Yet, despite being able to successfully change and save other features of the site, the custom CSS is not functioning on the site without being in Upfront.

What can I do about this? I would like it to function as it does in the Upfront editor. (Access has been granted for you to see what I mean.)

Thank you,
Jeremy