Potty training

My son is 4 and he’s autistic. When he speaks it’s only when he’s repeating something, so he can’t come up tell me when he has to use the bathroom. I have been trying to potty train him for so long and I’ve used different methods but nothing is working. I tried letting him go every hour, every 30 minutes, and that hasn’t worked. I’ve tried so many different things but nothing is working 😩 My other kids are potty trained but idk what i’m doing wrong with him because he listens to other things that I tell him to do, but when it comes to using the bathroom in the toilet he doesn’t do it.