Neff S5457X0. Drain runs constantly. No progress to wash cyc

Dishwasher drain pump continues to run constantly and does not progress onto a wash cycle. I’ve unplugged, pulled the unit out and removed the LH panel. Taken off the side tank and the lower mounted ‘overflow unit??’ fitted with microswitches/float and cleaned it of all the hard water deposits and other gunk. I note that the white tray has some water in it as the float switch, actuated by the red plunger is working and when I manually depress the red plunger the pump stops running. I’m a bit stuck now as to what to do. Doesn’t the drain pump also drain the water in the white tray? Or, do I have to remove that manually. Is this the reason the machine doesn’t go into the wash cycle or could there be additional reasons? Sorry for the long post but thought that I would include as much info as possible.

Thank you in advance.
Paul