Dog Won't Eat Dog Food

I agree have you talked him to the vet? Is it the same food you have feed him in the pass? Is there any reason that you can think of to course him don't to eat? Is he just old because if he is then maybe you need to soak the biscuits with warm powered milk so he can eat it.
Good luck and hope everything is ok with your dog.

Apparently you have given him scraps/human food in the past for him not to have a taste for his own food I'm guessing? If he has never had human food and has stopped eating dog food, then it is sick. It is not a good sign.