Mixer controls on VST instruments only works on 1st strip of port

(I apologize if this is already a question in the forum, but since “mixer vst instruments” isn’t allowed as a search on this forum because the words are too common, I am posting the question)

When I load external VST (Kontakt), the mixer shows a channel strip for each channel in the port. However, the only channel that shows a signal is the first channel. Adjusting the controls on all the other channel strips do not affect the playback. Adjusting the first strip controls all the instruments like a master control.

In this picture, all instruments should be showing a signal:

If I have multiple ports, the first channel strip of each port can be adjusted. This means if I want to control the volume of each instrument, I need to put them on a different port.

Thanks for any advice or suggestions.

This has nothing to do with Dorico but with Kontakt.
At the moment as you have it, Kontakt is configured to do an own mix and send out that mix to the first stereo out, which is the first input to Dorico.
So you have to change the setup in Kontakt so that it sends individual instruments to the other auxiliary output ports.