OMG, Kalani was exactly the same way when I brought him home. I actually thought something was wrong with him cause he was terribly shy and didn't seem to want to interact with us and only wanted to cuddle with Hoku (not play with her, just cuddle).
Well, that didn't last long at all - he is such a mama's boy and he loves to play with both me and Hoku! He's still a little shy with strangers but it doesn't take long for him to warm up and then he's just a little clown showing off. So, give it some time
Oh, as for the potty training, I didn't have to 'train' him with treats like I did Hoku - he just knew where he was supposed to go from Day 1 and doesn't ever have accidents