There are a number of issues that could cause breeding problems. Light at this time of the year is a big one, artificial light for at least 14 hours can help, something bright enough to say 'springtime sunshine!' I've noticed that my cats prefer the broad-spectrum light that my husband uses, perhaps that may help as well.
I have definitely noticed that does do have buck preferences. I had a doe I could not get bred. She ran violently from any buck. I had one day that I tried three different bucks. She bounced off the pen walls to get away. Until the third buck, my last choice, an albino. She loved him. Cozied up, lifted nicely, they were done in seconds. My husband had a blue Silver Fox buck that he really didn't want to use, as he wanted black kits. But, all the does loved him. When the other black bucks couldn't get the job done, my husband would put the does in with the blue, and they'd be bred in seconds.
Check the vulva on the does before breeding (the little 'slit' below the anus when you turn the doe upside down). If it is pale, whitish, dry and small-looking--she's probably not going to be interested in breeding. If it is pinkish, moist and perhaps a bit swollen--she should be prime to breed. A dark purple/pink usually indicates the doe is just past prime breeding, give her a few days and try again. I know that rabbits release eggs at breeding, and not in a monthly cycle like humans, but there is a mini hormone cycle involved, and the condition of the vulva lets you know where in that cycle the rabbit is. I'm sure the amount of light affects the cycle as well.
Next time you breed, try leaving the doe in the buck's cage, and take the buck back to the doe's pen. Hopefully, the odor of the opposite sex will entice their hormones. The next day, take the doe to the buck (who is in the doe's original pen), and try for a breeding. Whether successful or not, I take the buck back to his original home afterward, and try again a different day if needed.
Some report success by taking both rabbits to a neutral territory, and letting them romp together for a while (one used their living room, another a secure area in their barn) while under supervision. I have a friend that simply lets the two rabbits live together for a week, and hopes for the best. That can work, but if you have an aggressive buck or doe, you may end up with damage done to one or both of the rabbits. In a colony set-up, a buck is often simply added to the doe colony and the date marked down. One friend has had a lot of success with this method, even in the summer heat, as the bucks can sprawl over the cool concrete and keep their equipment cool.
If you live where it is hot, remember that temperatures over 85 degrees F for five days in a row, or over 90 for 3 days, can result in the buck being sterile for the next six weeks or so. If your buck has been successfully coupling, but not siring kits, has it been more than six weeks since your last spell of warm weather? Your buck may have had heat sterility. Some find keeping the buck in air conditioning, or using frozen jugs of water or frozen tiles in the pen will help prevent this problem.
Of course, an overweight doe will generally not ovulate--no kits even if they manage to breed. Diet and exercise can help with this