installing 48" deck on X320 problem

I am re-installing the deck after installing the mulch kit in it. I think I can figure everything out except for one detail. I do not know how to unlock the deck lift pedal. I did lock it by moving the pedal all the way to the back of the lawnmower. I tried pushing forward on the pedal, but it will not unlock. The height adjustment is set for the lowest position. I cannot see anything that is binding. This is my first time removing/installing a lawnmower deck. So I am a newbie at this. Please help.

Thanks,
bvollrath