It may be as simple as he is not ready to breed. My original Het Pied male was almost 1000 grams at 9 months old, and 1500 grams by 18 months old. However, he still did not breed until his third winter. Some of them just take longer. Also, he may be ready, and just not "compatible" with that female. I am not sure it works that way, but if your mom just dropped you in a room with a male human, you might not like him, and he might not like you. That is the best way I can describe what I think happens sometimes. Not sure if that is the way it works, but that is what I've told myself.