A pinkie is way too small of a meal for that snake. I'd move him up to hoppers immediately, and then after a couple meals up to adult mice. He probably could take a small adult mouse right now with no issue at all, but a more gradual change might work better.

Some snakes don't bother to strike & constrict meals that are already dead. Also, some won't constrict a live meal that is very small. They seem to know it can't possibly harm them, and it is possible some instinct is telling them not to waste the energy since there isn't enough calories in that meal to start with.

If you move up to bigger f/t, your snake might or might not start constricting, but either way is fine.