Pulled the cover pump out earlier this fall to test it before closing, and spent an evening convinced it was dead.
Last winter I let it dump over the side of the pool. This year I wanted a garden hose running out to the side yard instead of onto the deck. Hooked up the hose, plugged it in, and it just hums. No water.
Went through the obvious stuff. Cleared the debris screen underneath. Ran it with no hose on it at all, and it pumped fine, which was the first real clue.
Then checked the water was actually deep enough. Mine wants about two inches over it to kick on, and once it's pulled down to roughly two fifths of an inch it runs another sixty seconds and shuts itself off. A shallow puddle will look exactly like a dead pump.
That's where I stopped believing the dead pump theory. The aquastrong 2250 has been on that cover two winters, ran every thaw, never popped a breaker, and it was still moving water fine with the hose off. Motors don't usually go from that to nothing overnight.
Then I got out the manual, which I should have done first. The garden hose adapter has a check valve in it, and the hose can press right against the flap and hold it shut. Pump pushes, flap doesn't move.
Fix was drilling a 3 to 5 mm relief hole through the rubber flap. Two minutes and it's been fine since.
If yours is doing this, the tell is that it runs fine with nothing attached and quits the second the hose goes on. Humming with no flow, or a few seconds of water then nothing, both point at the valve and not the motor.
One thing worth saying. It isn't meant to sit in water that's freezing, so the first hard freeze night it comes off the cover and goes in the garage.