Males can be weird. I have one in particular that will not breed with a female if she is too big. Most of my females are 75-95grams, and he will gape and try to attack them. However if they are 55-65grams he is usually Okay, although still be weird and not a guarantee.
Try him in her enclosure, hers in his or neutral ground. Sometimes going outside can help too. And some males I feel only breed during certain times of the year.