Taken From the Manual (https://media3.neff-international.com/Documents/9000816278_I.pdf)
If the appliance stops during dishwashing or does not start for no obvious reason, first run the Abort
programme function (Reset).
Terminating the programme (Reset)
1. Open the door.
2. Press START button 9 for approx. 3 sec. until all displays go out.
3. Close the door.
The remaining programme sequence for draining the residual water takes approx. 1 minute.
Does it show the error when you turn the machine on, when you start the programme, or about 2 minutes into the programme?
It's either the outlet valve, the outlet valve AND the power module or the dispenser