NEFF S5443XI integrated dishwasher fills but then stops?

I have a 4 year old Neff S5443XI integrated dishwasher and over the last few weeks it has started making unusual noises and generally had become more noisy than normal.

The final wash that it completed took ~6 hours (!!) and since then it always stops when it has taken in water at the start of a cycle with no water movement inside the m/c.

If I reset the m/c and then start another cycle it just pumps out, takes in water and then stops again before any washing takes place.

I have checked the filters and they are all clean.

I have never worked on a dishwasher before so if anyone has a suggestion please spell out things in detail so I can have a chance of following the advice.

Any ideas out there?

Many thanks