Did you try to remove the pins from the front? In general they are locked from the front and you'll need a pin out tool that fits
Sometimes they are locked from the rear side, where the yellow seals are. If you aren't successful from the front, try to unlock them from the rear side. If you have one out you'll see how the locking mechanim works.
Sometimes they are locked on both sides. In that case you'll need a special tool:
