MIDI Import not working on Cubase Artist 14

Thanks. I concentrate on the initial post from you:

I get all the dispayed notes also to sound. I admit I have to mute the key switches notes in order to be able to hear the rest but then it is all there.

So the issue might be specific to your current installation and not a general issue.
Try to create a brand new profile please and start Cubase again. Here is an instruction: