the midi controller not connect to MainStage .but to logic it's ok.what can i do? please.

Hi

You need to assign the correct MIDI Port/channel for any screen control keyboard objects.

In Mainstage, go to the Layout pane, and select the keyboard screen control. In the Inspector on the left, click the Assign button and play your MIDI keyboard.

Switch off assign

Switch back to Edit or Perform

CCT