Wayne WPCP250 57735-WYN1 1/4 HP Automatic Pool Cover Pump with Magnetic Float Switch and 25 FT Pull-to-Shore Rope, Gray

I have had this pump for a month. Worked good at first. Now it cycles on and off when it is submerged beyond the indicated mark. Any ideas..

Is the pump fully submersible?

What do I do to make my pump start workinjg?

I have a plastic liner and then the mesh cover. So, do I put the pump on top of the mesh cover in the middle?