How big is he?? Did you brumate at all? I'm kind of having the same problem right now with my pastel lol. One of the things that everyone says seems to help is waiting til there is low barometric pressure (usually before or during a storm) and then putting them together. I guess it's just one of those instinctual things for them. Maybe because in the wild their breeding period is during the rainy season (I don't even know if thats true but that's all I can think of lol)? Just keep trying man. Patience is the key!