Possibilities, assuming the only light on is red too high.
1) The float is upside down.
2) The float was serviced (disassembled) and the bobber reinstalled upside down on the post which reverses the switching function.
3) The float or controller is being influenced by a magnetic field, it is a magnetic switch, if installed incorrectly in the magnet holder (wrong mount), a magnet is nearby, or the controller is receiving magnetic interference that could be a cause.
4) The float switch is broken, either broken wires, it is old and worn, or the magnet ring in the "bobber" is broken (visibly looks like a C instead of a washer). (This is very rare, I can count all the floats I have ever had to replace on my fingers)