Hotpoint Dishwasher HFE 2b+26 cn uk does not start

Last time it was running it stopped in the middle of the cycle and beeped 3 groups of one short, one long beep. I was able to run the drain cycle.
Now it will not start at all. It turns on, lets me select a program, but just gives me the beeps.
There are no flashing lights indicating an error code.
I've drained it, I've cleaned the filters, I've checked the water supply, I've 'reset' it by unpluggin it for an hour, I've made sure the door latches fully, I've checked the base for flooding. All clear and good.

identical to the Whirlpool WFE2B19

Neither the manual, nor hotpoints troubleshooting guide online give any mention to this error state. I'm stumped

UPDATE
A neighbour with the same model has had the same issue in the past and said he fixed it by slamming the door shut quite firmly. It's not worked for me but maybe a clue. I guess it's acting like the door isn't closed? It latches fully, and I've even changed the door switch but still no luck.
I've noticed a couple of small dents in the door in some areas where it would meet the rubber seal. Can it detect if a seal is not properly formed?

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