Indesit DFP58T94AUK… ‘door’ message

Hi All,
Having a problem with the dishwasher and am getting fed up licking plates clean, so thought about getting it fixed.
Simply put dishwasher will not start.
There is power to the unit, the display is working (am able to cycle through options) but when I press the ‘Start’ button, I get a ‘door’ message scrolling across the screen and that’s it.
Had a pretty good trawl through the web and can’t seem to find anything, foolishly phoned Indesit to see if they could explain what it meant, only to met with “did you want to book a repair ?” grrrrr….
I checked seals, obstructions, seating of door, closed it slowly, slammed it shut etc…
I opened the unit to check connections to door interlock – fitted a new one…. but still get the ‘door’ message scrolling across the screen.
I humbly throw myself before your collective wisdom…

The Old Bloke