Another hitch question

[sambam]

I have the new R20k Reese hitch and for some reason it doesn't want to release the pin. I am new to fifth wheels, so a little extra careful of dropping this thing on my truck. I lowered the landing gear and the pin came up a small amount, enough to convince me I am not still sitting on the hitch. I moved the locking arm to the unlock position and attempted to drive the truck out from under. The whole trailer wanted to come with me, so I raised the pin some more and it did the same. So, I went back down with it thinking maybe I was too high and still no luck. Since I'm new to 5ers, I don't know if it's my technique ( or lack thereof), or there is something wrong with this particular hitch. Due to other mishaps during the PDI, by the time I was ready to drive out of the dealership, neither I nor the PDI guy were interested in fooling around with the hitch. It seemed pretty staight-forward to me, so I left and now I can't unhitch. Any ideas?
FWIW, I have the Mor/ride pin box.