Toilet clog

I personally don't think the problem is a clog but probably a valve that is stuck in the close or virtually close position. Any "clog" probably would be lessen if the water was flowing. I also wonder if the snaking was really being done into the black tank but rather going up into the gray tank and that is why it could reach all the way in, not encounter any obstruction while still flopping around. If there was a poo-aper clog in or at the black tank end of things, something should have come out on the snake. But with nothing, the results don't match up to a clog but rather a valve along with a misdirected snake into the gray tank.