Check the float switch in the tank
If the float switch in the tank is above the water line then it looks as though you are using more water than what is going into the tank.
Stop using water from the pump and allow the tank to top up so the level switch is submerged in water.
If the the float switch is submerged in the water then please check to see if there is any debris around the float switch. If there is then please remove these as they are probably stopping the float switch from performing correctly.
Also check why there is debris in the tank because if fitted correctly the in-tank filter should not allow debris into the tank.
Did this help?