The older first generation always had a problem with the fuel display. My 2009 had been missing the first orange bar for a full tank for a decade since new.
It finally came back after using some fuel/injector cleaners, use the one’s with the PEA additive.
It might come back for awhile, go away. Who knows.
I assume you’re missing more bars. Mine comes and goes. At least I see it at times.
Back in the day, people were changing their fuel pumps 2-3 times under warranty and it still didn’t fix it. Which is why I never got it done, and just lived with that one missing orange bar.