Jura ENA 9 does not draw cleaning water

Hello everyone,
My ENA 9 is causing problems and I'm slowly running out of ideas. Perhaps one of you technical experts has a tip for me:
The machine no longer draws cleaning water and milk through the hose. Normal coffee is prepared and hot water also works. If the liquid had to be drawn, the steam comes out of the steam nozzle or the fine foam nozzle as normal, but the suction is obviously not sufficient to draw in the liquid. The amount of steam seems quite ok to me.
I have already tried the following:
- Descaled the machine twice (no improvement)
- Replaced the pump with membrane regulator (no improvement)
- Cleaned the flow meter (no improvement)
- Thermocouple on the thermoblock at 22,7°C just under 14kOHM
- Air intake nozzle replaced (the small rubber grommet) (no improvement)
- Solenoid valve opens and closes (otherwise no steam would arrive)
- Auto-Cappucinatore housing checked for leaks (is inconspicuous)
- There is no water dripping or steam escaping anywhere, not even at the outlet valve

There is not much more in the steam circuit, so I am at a loss. Any ideas?