I have the same problem. I dont know if your cat likes it, but some cats like eating grass. There are fountains that have a place for it to grow, and that might intrigue him. Otherwise, make sure your fountain is right next to his food, so he can find it when hes eating.
My cat, for some reason, would rather drink my filtered water FROM MY DRINKING CUP! (little *****..lol), so don't let him start this habit if he tries to. Keep putting him in front of it, every once and awhile, and encourage him. If he drinks - even a little praise like Jesus has come!
I've found it helps, when he feels like hes doing something right, he'll do it more.
Just be stubborn. Think like a cat.
Make sure there are no other places for him to get his water from, so hell have to drink from there.
And! Try turning the "waterfall" on high, if you can. We have the drinkwell, and I find my kitten will go look to play, and then end up drinking instead...