So it will come out except sideways, so you want to solve this when the tank is empty of "black stuff".
Keep pouring in water to the tank from the toilet until it comes out or jams up sideways. If it jams up you poke at it up the dump end to turn it so it will come out.
If you leave it there and now you have a tank of black stuff instead of just water, and then try to poke at it to get it the right way around, you will not enjoy that!
BTW we never use those little bottles of blue stuff. Just add laundry soap after each dump. No smell, no problem.
1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.