Does the Fuel gauge work at all? What's it doing or not doing?
Disconnect the (Yellow) wire from the sensor and connect it to a jumper wire that is electrically grounded to the body of the car.
Turn the ignition key to ON or ACC and watch the Fuel gauge to see what it does. It should go to Full fairly quickly.
If it does, the gauge and wiring back to the tank are working. Turn the key switch off.