Problem with water / coffee circuit

De Longhi Magnifica S

I switch on the coffee machine. In normal operation, the preheating and rinsing process now starts and a little water flows into the cup, the two green LEDs next to B4 and B9 light up and the coffee machine is ready to start

Now, however, the water is heated up, but then the pump does not seem to generate enough pressure or the system is blocked somewhere and no water flows into the cup. The following error message is displayed:
- coffee grounds container indicator light (left) flashes.
- water tank indicator light (center) permanently on.
- indicator light (!) (right) flashes.

P.S. Descaling was always carried out according to the instructions for use.

I hope that someone can help me with troubleshooting so that I can drink a nice cup of coffee again. Thank you.