bosch dishwasher not filling with water?

My Bosch dishwasher runs through its cycle but no water seems to go into the machine. I have taken the left hand panel off the machine and can see that the water is coming into the reservoirs at the side of the machine but something seems to be preventing it going from there into the interior. Any ideas? Other posts seem to suggest that it could be something to do with the "floats", but these do seem to move up and down ok.