First at ll, sorry if my english is bad, I'm from Menorca, but i will try to explain the best I can:
Maybe is due to the arm selector. It is a little motor at the bottom of the dishwasher, attached to a gear that turns a circular pattern with holes.
The worst thing is that you must disasemble lots of parts to arrive at this part. You must remove the top cover, both sides, and then loose the springs that close the door. Then you must take off the bottom.
First check if the wires are firmly connected.
This is a image of the part that must be broken:
https://zipten.ru/image/cache/catalog/644996-1-1000x1000.jpg