The miles notification on my 2010 Scion xD stopped working?

I have a 2010 Scion xD and live my the notifier that shows me how many miles of gas I have left until I am empty. I just got it inspected and after that when I put gas in my car the miles did not increase. So it now shows I have 0 mile sod gas left even though that is not the case. They want me to go back to the dealership, but I am irritated that I didn't have the problem until I took it there!! Any ideas?