Sump pump only turns on when I open the lid - working ok?
It's likely that the flexible output hose is interfering with the pump float. When you close the lid the hose flexes into an S shape, laying on  top of the float.
The best solution is to eliminate the flexible hose in that area and replace it with rigid pipe, but you can also secure the hose in such a way that it can't settle like that. Make sure the lid is installed with the hose to the opposite side of the pail from the float.
One thing I've done is to use a couple bricks in the bottom of the pail to maintain the pump's location. If it vibrates its way over to one side the float can get stuck that way as well. Put some bricks below the float area to prevent that.
Were that my home I'd get a garden hose down there and flush/scrub all that algae out of the pail and off the equipment. It can't be smelling too great. Flush the area until the water is clear, and remove any large debris that remains.
At the start of the dry months, when the groundwater is no longer flowing, lift the float and hold it until you hear the pump suck air. This will dramatically reduce future scuzz growth. You could also pour a small amount of chlorine bleach in there.