if working correctly...the trunk can be part of the central locking system...or disconnected from the central locking system.
It all depends on which way you position the trunk lock. If you leave it in a horizontal position ( -- ), you have disconnected the trunk from Central locking and the trunk will have to be unlocked with the key.
If you leave the key in the vertical position ( | )..then the trunk should lock/unlock with the central locking system
Read the text in the right column titled "Secure Seperately":