Unfortunately, it may take some time and patience and you'll have to keep your "eye" on him until he gets the hang of it. We got Choppi when he was 12 wks old and he was pee pad trained but still had problems going on the pad. So we had to basically retrain him all over again. Of course new house, new environment, new parents and dogs around him would prob scare him and I took that into consideration.
I made sure he was never left to "wander" about and took him to the pee pad every couple of hours. I made sure he'd do his business before getting off the pad when we woke up every morning. Gave him lots of praise and even treats when he went on the pad. Eventually I weaned off the treats and just gave him lots of praise.
My sister had a similar problem with her Maltese who would wait til she got inside to do her duty. It took her some time, lots of patience and lots of waiting outside for awhile til she did her duties, her Maltese slowly but surely picked up on it. It may take awhile but hang in there!
