You can attempt a reboot and a re-calibration. But, it may be a sensor failure. It can also be a connector failure. The wires use the same connectors that telephones use. If they get wet, corrosion follows.
As far as I know, sensors are no longer made. There is a company, See-Level, that makes a product to measure the level differently and it is advertized to plug into the Aladdin system.
In practice you can do without. The tank is 60 gallons. For us, draining every two weeks seems to work fine. I've also learned that there is a slight change in the sound when flushing if the tank is almost full. When I hear it, I know I forgot my two week cycle.