FM won't save modification I make to Settings file

While working with my settings file for an HTML5 output, I wanted to make a few basic changes to the template layout (font/header color). I output to test the changes, and nothing changed.

I went back in, made the changes again, and then opened these settings to see if they "took," and the options displayed the default settings.

Any ideas for what is blocking my modifications from saving?

Thank you.