I increase the volume of these programs to the max, but when i click another part (ex: piano) in VST Live and come back to the String part and open the Halion 7, the volume is seen reset to the marked position.
Then, you see that you have a MIDI Volume programmed in the Layer which will be sent to the instrument when the layer becomes activated (when its Part becomes activated).
If you want to maintain those values in Halion instead, ctrl/click the orange MIDI Fader in the Layer to “Not Set”, so to avoid it sending those values. The same goes for pan.
Today I had the similar issue with another layer. In this case whenever I close and re-open the project, the Halion volume is resetting to zero inside halion.
I think this issue starts happening, whenever i press the CONTROLS to switch to MIDI, to check if the volume is NOT SET and then switch it back to AUDIO
VST Live does not send anything if “Not Set”, which is also the default (ctrl/click).
But there are multiple possible sources that may send MIDI to your plugin, shared, global Part, MIDI track etc, make sure to exclude all those.
When operating this switch, the actual value of the selected type (audio, or midi) is updated. It would only ever send something if that value had been changed.
You may send a simple project (just the .vlprj file) for us to examine, if you still encounter this behaviour.
Even if the volume is increased for that layer inside Halion 7, still this need to be in monitor then only sound will be heard from that layer when the left zone keys are pressed.
And if you expand (click “e”) the “Song 1” Channel, you can see the MIDI Channels, again some are “0”, not “OFF” (standing for “Not Set” and “not sending anything”.