The thing is, female panthers do more than just switch on or off from receptive, they also cycle infertile eggs as well. So she may be working through an infertile clutch and that's why she's not interested. Being able to see a male can send females into producing an infertile clutch, so if they could see each other before they were placed together you may have missed a window. Or she's simply not ready to mate yet (you haven't told us how old she is).
You can't force them to mate so you'll just have to wait until she's ready. She will be, sooner or later.
Do you have a laying bin in there just in case she does have infertile eggs at some point?