A trigger can only be activated when the player enters the same space that the trigger occupies. (i.e. The player touches the trigger, and it activates that way.)

If you want something the player can activate by using the action key ("F" key), you should use a SlidingSwitch instead. Just make sure you bind a brush to the SlidingSwitch, so the player has an object he can interact with. The SlidingSwitch itself does not appear in the map.