Oh Buffy I feel your pain. DS8 was awful stubbon it was a nightmare. We tried aiming at the cheerios and m&m rewards nothing. Finally one day he was using his brothers computer and I said to him if he wanted his own he had to use the potty. that did it he trained himself in 3 days. Course I had an old crummy computer that was fine for kids games sitting in the basement.
Hang in there.
Hang in there.