Original radio install

[Bozstin99]

I have a 2017 berlingo I’ve just purchased and it had an aftermarket double din installed. I’ve removed and tried to install the oem touchscreen radio but it’s like the harness isn’t long enough to be plugged in. Does anyone know if I’m missing an ‘extension’ that might have been removed when they put the aftermarket unit in. 
Also there’s a socket on the back of the unit thats not being used is this normal 
Thanks