To start with the tank you see at the bottom with the orange bits in is normal as this is the water softner so that's ment to look like that,
As to the 7 flashes this means the pressure sensor isn't picking up the water level even though the flow sensor picks up water is passing through it.
This is usually the pressure sensor in the sump rather then the flow sensor in the filling tank. If you only ever got 6 flashes then that is usually the flow sensor but 7 flashes is usually the pressure sensor.
What you can try is remove the bottom basket and the filters in the bottom. Then look in there you will see a round black grid. This is the pressure sensor. Pore boiling water in there and then with an old tooth brush give this a scrub as they do block up in there.
Then retry it and see how it goes from there. Fingers crossed that cures it.
But if its still the same then remove the outer door panel and there you will see the wiring look running from the top to the under side. Give each a tug and check for a broken wire in there as the wires do like to break in there.
If the wires are fine then you need to remove the pressure sensor from under the dishwasher and test the switch in there as its a microswitch. If faulty then you need to replace it and that should cure the fault from there.
Try that and see what you find from there. As the 7 flashes is mostly something to do with the pressure sensor in there.