I am needing some advice on the new doggy door we got Saturday Oatmeal,Kasumi,and Elmo use it just fine but Otis won't he just sits there until you go over and lift the flap for him to come in I don't know if he is scared of it or he just likes the door being open for him we have tried lifting it and showing him that it won't hurt him and when he comes through praise him really well with voice,rubbing,and treats but nothing works i was wondering if anyone had any suggestions on how to make it easier for him. Thanks