The fact is that she may be in heat yes, but she clearly isn’t receptive to him. She’s not far enough into heat the she will let him mate her. Plus they only ovulate near the end of their heat cycles. The way you can tell if she is near is when her heat blood becomes more pink/clear.
They tried to forced the female to mate by putting on her on the leash and holder her in the same spot but they let her go unsuccessfully that’s my opinion and I also think making her stay in that cage thing area it’s obvious she DOES NOT WHATTO MATE