Have you tried pee pads? They work well for us. We never used a kennel. If you put the pee pad near the door, when he goes to it, you can let him out. YOu can buy a spray to spray on the pad that is suppose to attract them to it also.
How long do you keep him in a kennel? That may be part of the problem, if he is in there for a long period of time.
Good Luck with your training..... it does take time with a Yorkie. They can be little "buggers" to train.
Anyone else??? Can we help this gal out??....... We know that it can be frustrating!!!