This Info / write up courtesy of Charlie716 from the
The problem is that the rear seats have sat unused for a bit and
when lowered into position, the back wouldn't lift up.
First task is to remove the upper cover by removing the single posi drive
screw that retains it.
You will then see this
The problem I had was in the down position, as the seat clicks into the
locking bar on the boot floor, the locking pin shown should move in the
direction of travel indicated and release the locking cam to allow the
seat back locking plate to move as the back of the seat is raised.
Mine didn't move far enough so the seat back remained
The locking cam is what is on the other end of the
operating rod from the handle you use to fold the seat back down.
What I did was lubricate the surfaces of the pin and locking cam with WD40
then operated the seat a few times and it all freed up nicely.
Replace the cover and this is what you have.