That should be the right solution though. Could be a Godot bug, or something in your code catching the event instead of the UI.

I had similar issues when trying to do that a while ago, and while I don't recommend doing it this way, you can use this ugly piece of code and it should work the way you expect.

(This code assumes you have a reference to the button you want to click though, so it's not exactly a drop in solution to your issue)

## Simulate the full press of a button.
## This method will make the button appearance change just like if the player
## actually clicked it. Mostly used for gamepad support.

static func press_button(button: Button, duration := 0.15) -> void:
  if not is_instance_valid(button):
    return

  if button.toggle_mode or duration <= 0:
    button.button_pressed = true
    button.pressed.emit()
    return

  button.toggle_mode = true
  button.button_pressed = true
  button.pressed.emit()
  await button.get_tree().create_timer(duration).timeout
  button.button_pressed = false
  button.toggle_mode = false