Black water tank completely full and won't drain. Help pls.

Yes I have already disconnected the cable and have been operating it manually. Tapping and shaking the tank has loosened up some of the waste. I have a slow trickle coming out when I agitate the tank but that's it. I dropped this hole straight across from the stem, but I pretty much push the wire all the way in without being able to feel the gate. With a post pardon wife and a new born, it's getting to be a bit rough. How thick is the gate, and is it not actually centered in the valve body? It's a valterra 3in gate.