There is a baffle in the tank that sounds like has come loose holding the sensor arm up. I would start by removing the pump and inspecting the tank. Also you can check if the float arm is working when the pump is out. Here are some diagrams to help you get the job done. (Below)
Please let us know what happens, we are interested to see what it is.
Images (Click to enlarge)
Wednesday, August 16th, 2017 AT 12:06 PM