Your rig has probably been sitting around for a while and it will take time to figure out the systems and how to properly operate them. The tanks are one one the things that people complain about the most. All of the suggestions that have been posted are good ones. Just have patience, do one thing at a time until results are noted.
I think that the driving around bit is wasted energy. There was a youtube clip where the author showed the results of all the methods expressed above (except the power cleaning) using clear tanks. None of the methods resulted in a clean tank. The tanks are going to stay not clean. The best you can hope for is usable tanks that do not smell. I use Happy Camper as well.
Lastly the black tank is not a septic system. It is a private porta john. Nothing stays in there long enough to be eaten by enzymes.
2007 Fleetwood Bounder 38V