[Richard and Rhonda]

First of all Matt is spot on. I also have pulled a handle loose from a paddle. How does one get the paddle out you say. I threaded a large bolt into the paddle and pulled it out that way. Can you snake a wire hanger into the tank? If not, you may not have actually opened the valve. Two screws and you can remove the top of the valve and see where the paddle is.

I would try plain old detergent first. Like dishwashing detergent. You need to hydrate and dissolve the clog.

How much water is in the black tank? Do you have a sight glass hose somewhere. Look on both sides of the tank.

Do you have access to a black water drain that slopes into the drain? if so put on your rubber boots and gloves and have at it.