That electronic gadget may or may not be very accurate. Don’t over rely on it. I would refill the tank after you get to about half. You may get lucky and somewhere between now and when you finish filling it up from half full, it will start working again.
There is also the possibility that the gauge has problems that are going to take some real repairs. That could include removing and maybe replacing the float valve assembly and I don’t know how difficult that is on your car. It may also be a loose or broken wire.
Hopefully someone who knows Nissan’s better than I can give you some more specific help.