He probably needs time. When they are ready you rarely need anything more than an intoduction and some quiet time.....some Marvin Gaye or some thing won't hurt either. I had one male last year breed at 4 months and about 420 grams and I had one the same year that wouldn't lock any females til he was 8-9 months and around 650. Just keep trying all the tricks and he will when he is ready