Nuendo 15 does not track external MIDI input

Nuendo
1

Action:

Playing a MIDI note on an external controller keyboard.

Result:

1. External MIDI is indicated graphically by the meter in the lower right corner.

  1. MIDI is not detected by the inserted MIDI Monitor.
  2. No MIDI passed into the selected instrument track.

Background info:
I use Windows 11 with the current MIDI 2.0 update.
Cubase 15 works as expected, although it showed the same issue right after the Nuendo 15 installation (fixed by unselecting all lower tic boxes in the “Studio Setup/MIDI Port Setup).

I opened a working Cubase 15 session in Nuendo 15. Didn’t help.
I reinstalled Nuendo 15. Didn’t help.

Now what to do?