Changes not saving and reverting back to theme defaults

I have been using the Fixer theme in Upfront and I am trying to customize it. I make my changes and hit the green "Save" button and it says "Saving" and then "All Done", but if I exit Upfront, none of my changes are actually saved and the theme defaults to its out-of-the-box design. Needless to say, I am frustrated that I put work into it that's now gone.