The keypress action is specifically for keyboard keys. It appears you do not have a keyboard key bound to that control.
What you could consider is to bind the secondary action to a keyboard key, and to use the gamepad trigger (which I believe should register as button 12, assuming you've assigned your gamepad to a VoiceAttack joystick slot, of course) to trigger a VoiceAttack command, which in turn presses that keyboard key.
To have the keyboard input "follow" the button input from the gamepad, you can set up two commands: One with the "Shortcut is invoked only when all buttons are released" option unchecked, which contains a keypress action set to "Press Key(s)", and another with the "Shortcut is invoked only when all buttons are released" option checked, which contains a keypress action set to "Release Key(s)".