Neff Integrated Dishwasher – pump constantly running

Hello,

I’m helping out my father-in-law who is having problems with his integrated Neff Dishwasher (sorry not sure of the model). I’ve tried numerous things to fix it and have run out of options apart from having a professional come look at it – does anyone have some suggestions to help identify what the problem could be?:

– The pump is constantly on, there are no error messages (the device doesn’t have an LED display) & the drain LED is always on. Water at the bottom of the dishwasher doesn’t leave the system at all.
– There’s nothing obviously blocking around the filter, which is clean, and I’ve used baking soda/vinegar/hot water in case of blockage
– I’ve used a drain cleaning pipe and can’t see any obvious blockages within the waste pipe. There isn’t any resistance and I can push quite far
– I’ve checked the waste pipe and it seems there aren’t any cuts or knots that are causing a leak or block. When I’ve looked on the other end of the pipe (under the sink) it is bone-dry and dirty (i used the drain cleaning pipe on this side — and again, didn’t run into any obvious blocks)
– I’ve taken off the bottom and there isn’t any water that has leaked into the base
– I’ve taken off the left-hand side panel and the “red rod” looks fine, no water or debris in the float
– I don’t see anything move within the water inlets when the device is turned on (i do see quite dirty water connected to the waste pipes though)

Any help would be greatly appreciated – I’ve ran out of ideas on where to look next!!

Thanks
Tom