Go around the car opening and closing each for in turn
Don't forget the boot lid as well as the bonnet

As fan days, the not switch is the easyest to get to buy they are all fiddly to change

Of course there is always the possibility is a broken write in the boot hinge as well as the master control in the drivers door, just because a replacement comes from a "working" car doesn't mean it will work

You may also need to reset the gem unit as sometimes these play up setting as they also control the central locking Gubbins remotely