It sounds like that there is inadequate water pressure getting through to the dishwasher. Turn on a cold tap and see if there is a good flow of water. You may also have a piece of debris in the flexible pipe that supplies it with water. If the water pressure is low, all over your property, the utility company may have a leak in their supply.
I had a similar problem on a Bosch dishwasher that was not that old – besides checking the water supply to the unit, there is a small metal gauze filter at the inlet that may be blocked.
I could find no water supply issue with my Bosch dishwasher, so it went in the bin along with Bosch’s reputation for making a reliable appliance.
Thank you all for your responses. I haven't got the manual as I've moved house and inherited this dishwasher with the property, and googling didn't help either. However, the links and videos highlighted in your answers will, I think, solve the problem. Many thanks all.