Hello i am new hear and my Wifes Citigo which i drive as well 2013 has the following probelm

The rear lock sometimes works on the fob. Button also not seeming to work. Anyone had this problem.

Key fob works two ways:

press to unlock

hold for approx 3secs to unlock and release 

 

Might be worth ago to see if either of those ways work

Thanks Jonny, turns out its the button that is faulty. Water has been coming in through the wiper gasket. I can open it by press and hold the fob and at the same time pull on the door like you said. Button proved faulty by bridging the plug to the button.