C4 Grand Picasso rear seat not folding

[knappettg]

Cord A in the pic does nothing on the near side rear passenger seat.
It folds the seat back on other seats.
Pulling the cord at the back from the boot moves the backrest a few degrees but not fully.
Is cord A attached to something behind trim B, C, or D?
If so, how do I remove B, C or D to access it.
Or is it a different problem entirely?

[GiveMeABreak]

It just says to pull 'A' in your diagram firmly upwards.

[knappettg]

Yes - but nothing happens. It seems it is detached from whatever it was attached to.