ATO on Nuvo SR 80?

The Smart unit didn't pump when the SC was outside the back wall of the sump, or on the narrow wall between the sump and the main tank. When put outside the glass on the main tank it won't stop pumping; it has over filled all of the chambers in the sump area. The sensor unit is now completely submerged in the tank itself. SC has a steady green light. The ATO emptied the entire 5-gal. reservoir and now the pump is whining loudly - even after adding a gallon and more- and the light is still steady green tho the pumping has stopped.