I had this issue some years ago. Happened to me, of course, just as I was leaving for a road trip, with the low fuel warning, even though I was nearly full. My first thought was that I'd be screwed figuring it would trigger the defueling mode after so many miles.
Anyway, it's most likely, just an intermittent/dirty connection. There is a plug somewhere on the driver side of the tank that is the connection of the sender into the harness. It lives in a pretty harsh environment. I pulled mine apart and plugged it back in and went on my merry way, with no further issue. I eventually went back and sprayed out the connectors with some CRC QD, to make sure the problem didn't recur.
2006 Ford E350 6.0 SMB 4x4 Modified EB45