I have heard that when puppy's are teething they do not eat as much kibble because their teeth and gums are sore. As Mordy has said trying wetting the food with water that may help. Make sure to read the directions though because some foods, like Eagle Pack, tell you not to soak with hot water or to microwave so keep an eye out for a label that may say something like that.
That's what I meant about soaking. Sometimes I don't type what I mean though and it comes out wrong, thankfully Mordy is here to correct it. Some foods don't have any warnings or say not to microwave the food or use hot water to mix and serve with though. The eagle pack is the only food that I have ever fed that says not to microwave it. I know when I was younger my uncle fed his dog gravy train and he would mix water in it and microwave it for her and she never got burned (or maybe she just didn't tell anyone).