I had to update the link for my Prius after the major update on Fuelly, you probably need to do the same. SCH-I535
I didn't have to do anything, after the Fuelly site update, icon still working. Well, unless Alzheimer's setting in...
Of my two icons in my sig, the Camry one worked after the Fuelly site update, the one for the Prius had to be updated.