Water quantity for Impressa XS90

Need help!

Had purchased a used Jura Impressa XS90. Works wonderfully. Now I wanted to change the amount of water for espresso according to the instruction manual.
There it is:

Open the programming door and press the Rotary Switch until the signal sounds. Then a menu should appear in the display (filter/water quantity). The signal sounds, but the display doesn't change - even if you turn the rotary knob.

Am I doing something wrong?

Yes, that's actually correct. Press and hold Rotary to enter the menu. And then navigate through the menu by turning it. What if you turn it after you've held it down longer?

No - that's the problem.

It's called "Please select" - I keep the button pressed - the acoustic signal comes too - but the display doesn't change....

I've tried with the button pressed as well....