Mine slides ample amount to get in/out of back. Maybe the rails have got out of sync. Try the following:
Tip seat back so its in the forward position (ie to let someone in the back)
With seat still in this position, slide the seat back as far as it will go.
Now click the seat back into it's upright position
Now slide the seat the seat forward to the required passenger seating position using the back and forward seat adjuster at the from of the seat (as you would to adjust the distance from the dash if sat in the seat).
Now get out of the seat and try and tip the seat back forward and then the seat should slide towards the front of the car giving the required space for the back seat driver to get in