Here is an excerpt from an article by Bill Strand at the E-zine that might help with your pairs breeding troubles.
4. Introduce a cricket to get breeding
This is one of the stranger ones, but...Sometimes when a female is introduced to the male's cage they do nothing but look at each other. When faced with this situation I send a cricket running through the cage. One of them will go for the cricket, and, for some reason, this disruption will break the tension and breeding starts. It doesn't work all the time, but it has worked enough times that I am willing to call it a hint!
5. Give a man his self-confidence
I once had a male Jacksons chameleon that had a self-esteem problem. I would put a female of an appropriate size with him and he would shrink away. She would show no agression, but he was acting the equivalent of a dog with his tail between his legs. Could it be due to the fact that he was the smaller of two males that were kept together for a while? He was the submissive one and just never seemed to snap out of it. I tried getting him in the mood by showing him another smaller male. This would send him running. This guy had a serious problem. I tried to give the guy some confidence by showing him another male from a distance and as soon as he got sight of the male I would take the intruding male away. I kept this up once a day showing the male longer and closer to the patient. Each time I would take the intruder away right at the point that the patient would make a move to turn and run. So each time the patient successfully "defended" his perching branch. I started using a mirror as I got got closer to the patient (no need to give my helper chameleon a loser complex). It only took about a week before the patient would stand and fight and appear ready to attack the mirror. The mating after that performance was successful.
If you want to read the whole article, here is the address:
http://www.chameleonnews.com/year2003/jan2003/hints/hints.html
Panthers breed in spring and summer in Madagascar, so you could try lowering the temps 5 degrees or so for a couple of weeks and raising them up again to simulate a seasonal change. I have encouraged my outdoor panthers here in South Florida to breed in the winter time by using a low wattage heat lamp in the female's cage for a week to bring the temps up. She changed from dark non-receptive colors to a solid peach and accepted the male shortly afterwards.
Also, what technique are you using to introduce them?