Hotpoint SDL510 3h/6hr flashing. Clear drainage pipe, water inlet filter & impeller.

The Hotpoint SDL510 is making a very loud noise as if it’s pumping but none of the water will drain.

I have manually cleared the water, checked and cleaned the filters inside the normal washing area.
I have replaced the water inlet pipe with a different one (I had spare) and checked the filter on the inlet, no issues there.
I have checked the drainage hose and that is clear of obstruction.
I have remove the bottom and checked the impeller, seems clear, though a little hot (maybe this normal?)
I then righted the dishwasher and turned on again to check. The noise comes back and the issue remains. With only a little water in the bottom I can hear it is sucking. The water level though does not drop.

So – think the impeller is fine, it’s at least clear. I can hear the dishwasher is sucking, so seems it is trying to drain, but the water level doesn’t move.

Can anyone advise what my next move might be? Other than buy a new one…

Thanks so much in advance.