We had the same problem. There are no words in our vocabulary to explain how it feels when you need to go to the potty. And so there is no way to verbalize the directions. It takes the child noticing the sensation each time.
Our daughter was a child that was always so fast to do everything, but the potty, was not anything she was interested in. Walked unassisted by 6 moths, spoke in full sentences by her first birthday. Her comprehension was off of the scale..
Now imagine, I tried everything. we even had little twin neighbors that were potty trained by the time they were 1 year old!.
But no matter what we tried.. no luck.
She finally figured it out on her own.
I have learned that this child cannot be bribed, prodded or forced to do anything. She is still like this and is now 22..
At day care in the 3 year old room the little potties were all lined up and she finally at almost 4, noticed the kids sitting there looking at books sitting on the potties. So she gave it a try. Sitting there until "the potty came" an some how it clicked for her.
So my suggestion is to give it a rest for a few weeks and then see if he if he is interested. Ask the teachers in day care what they suggest, they spend a lot of time with your child. I bet they can offer some suggestions.