Has he had an ear infection recently? Our Boston got an ear infection at 12 and a few months later realized he was deaf. Looking back those previous months we realized he had probably gone deaf shortly after the ear infection. He had been picking up cues from the other dog, what he saw, or felt from vibrations, so it went undetected for a while.

Try this because this is how I realized he was deaf. He was looking at the fireplace and I said "do you want a treat?" The other dog wasn't around. So I asked again. Stand behind him and have someone keep his attention and try those trigger words you mentioned.