Whirlpool Duet Sport error code f-21. Cleaned trap, but still nothing

Hello all,

The F-21 codes has come up a few times through the years, and cleaning the trap usually fixed it. Last week we had a service call to replace the tub seal, and all was well, except we notice that the power on buttom(upper left of front of thew machine) was push in further than before. Now a week later the code came up again. Opened it up and this time found that nothing came out except a few gallons of water with no coins/ pins etc... at all. It's almost as if the pump next to the trap isn't working, thus the water is backing up and tripping the code.

After closing it up I tried it again, and I get a humming sound from the machine, and it will spin, but the code just comes back on.

Any advice?

Thanks