I have an older under-sink sump-pump in the basement of a rental property. It is used to drain the laundry tub. It used to go on/off automatically when there was water in the sink, but now you have to turn it on/off manually, which is a major pain for doing laundry!

Are there any common causes/solutions for this? In case it helps, its on/off switch is on a cord - when it is plugged in, it goes on regardless of whether the switch is on or off...

Thanks!