Ha! Just went to post this and I see that MSD has got in ahead of me, as usual! :lol: I'll post this anyway although there may be some overlap.
Female rabbits don't really cycle... They are induced ovulators, which means they release eggs as a result of sexual stimulation. I assume you have been checking the colour of the vulvas and that it has not been the deep pink/red/purple that often indicates that the doe will be receptive.
There can be a number of reasons for lack of interest in breeding. Sometimes it is nutritional. Vitamins A and E are essential to both breeding interest and breeding success. These nutrients are added to the pellets, but are vulnerable to loss from heat or prolonged or poor storage. You can supplement the rabbits for a couple of weeks and see if it makes a difference. Good sources of Vitamin A are dark, leafy greens such as
parsley, carrot tops or dandelions. Phase them in slowly if you do not normally feed greens. Vitamin E can be added with some BOSS (black oil sunflower seeds) or wheat germ. Most rabbits prefer the BOSS. Again, start with no more than a teaspoon increasing it to two teaspoons per rabbit per day BOSS can be fattening so don't overdo it.
This brings me to another possibility. Sometimes if overfed, does accumulate fat around their organs in the body cavity. This can make it
difficult for them to conceive; it can also make them lose interest in
breeding.
Other things to try: 1-2 Tablespoons of REAL apple cider vinegar added to each gallon of drinking water. One off-beat suggestion that some breeders have found helpful is to offer the rabbits a bowl of Celestial Seasonings Raspberry Zinger herbal tea. We don't know why it seems to work in so many cases, but definitely worth a try if the does continue to be stubborn.