QuickMill 05000a does not produce coffee

I bought myself a used QuickMill 05000a and first adjusted the grinding strength and water quantity until I thought the espresso was perfect.
The next morning I wanted to brew an espresso and suddenly the green "OK" lamp stops blinking and I can't brew an espresso. What could be the reason?

I have already noticed the following things:
Hot water via the steam tap works.
Water steam via the steam tap works.
beans are ground when the steam tap is turned off and the 1st switch is pressed.

I have already cleaned and descaled the machine and am now helpless : /

Has anyone an idea?

Greetings,
Patrick

Hello,

When the steam tap is swivelled out, the coffee buttons should have no function. Otherwise the microswitch may be defective.

Grüße
Kai