Unable to open the Trunk

[Estam]

Similar to last post having an issue with 2011 conv 200. Sometimes it opens and sometimes it doesn't but when it doesn't open when pressing the button it makes a clicking sound behind the dash so assume the button is operating just not doing its job. Felt for a while it was the method of locking the vehicle, using the fob sets the theft alarm and the button no longer opens the trunk. Using the lock button on the door enabled the trunk button to still operate. Hope someone can shed a light on our problems. Many thanks...