Durango 1500 Black water holding tank drain problem

Hello,

We're camping in our 2011 Durango 1500 at a camp site with full hook ups. The grey water holding tank has been filled and drained twice without any problem, tonight the black water holding tank is full. I pulled the drain handle and nothing happened. The grey tank still drains fine but the cable for the black tank drain doesn't seem to be attached to anything.

Can anyone tell me where I can find the valve that the drain handle operates, the bottom of my trailer is enclosed and I would like some advice before I start to take things apart underneath.

Any help would be appreciated as I have to check out tomorrow and need to empty this tank before leaving.

Thank you in advance