The Marquis is similar to the Patriot Thunder in that both use a powered drain valve (same as the black/grey water tank drains). However since your Aladdin says the tank is full when it is not, the tank level sensor probably went bad. It is a "pressure sensor" that screws into the bottom-side of the tank and uses a telephone cable type connector. These are available and easy to change.
If your Marquis is like my PT, the water tank is in the front right compartment next to the AquaHot unit. And the sensor can be reached from the next compartment back.
The water fill is in the Wetbay (and on the switch panel in the Kitchen). Perhaps the Auto Fill switch is bad (since your not seeing the "AF" in the Aladdin). Try using the switch in the Wetbay compartment to turn on the Autofill.