We have a CDA WC140IN Dishwasher which today is giving error 1,2, 5 which usually implies a water input issue, or blocked filters. It doesn’t appear to be either of these, but clearly a blockage somewhere in the system.
What we have tried?

1. Starting a new cycle, we first hear the pump emptying any residual water, then a 2 minute wait, before the water inlet starts (feel the throbbing in the inlet pipe), that stops, then the machine appears to briefly start before stopping with the above error. Filters are clean as a new whistle. There is no water in the machine other than the salt chamber, the arms don’t move (and are not blocked). However when I remove the top of the salt chamber, water which appears to be under pressure floods out. Not an expert, but does this indicate a blockage after the salt chamber?
2. We have siphoned out the water from the salt chamber. Put some hot water in to see if this could ease any blockage. No joy.
3. Previously to this error, my wife had added some proper dishwasher salt, and maybe used it 2-3 times since without an error.
Question is there a simple way to resolve the blockage?