When I first brought Issy home she would have a few accidents too but there would be no warning; no circling, sniffing, nothing. I just tried to be very consistent, use the same door to go outside (in my house there are two), and I let her out a bit more frequently. She would also use the bathroom in her crate, so I got a smaller one for her and that worked like a charm!! One day it just clicked, she kept walking from me to the back door and ever since then she has been fine. She's now starting to talk to me if I'm asleep so I wake up to let her out (Daphne taught her that), before it was a full body slam!!
He'll get it, it will just take a little while. Good luck!