Four months and no progress means either he's in a diaper at home or parents aren't being consistent and are just cleaning him up.

For me, that's the time I terminate. I've never terminated a child but I have terminated parents who intentionally are sabotaging their child and my efforts. They began this toilet training and we not invested in it. The moment it became inconvenient to the adults they quit on it.

I bet you that child is in diapers at home.