My 4 year old son is nonverbal, diagnosed with level 2 autism. I've just started an attempt at potty training, but with not much success. He will sit on the potty but very briefly. He shows no sign that he has to "go" and is not bothered at all by a full diaper. I've tried setting a timer, offering rewards and set up a little potty area with books but I'm not having much luck. Any tips or support would be so appreciated!