Yeah, I'm in the same zone in IL as you. I don't have any clusters at all on my vines. I keep looking at the "joints" between the main stem and the leaf shoots to see if any flowering buds look like they're starting, but all that are showing up are more leaf shoots.
Can't figure out why yours are OK and mine got frostbit....unless your temps stayed just warm enough that it didn't get them. This is the first year they haven't produced, and I just know it was those two below 35 degree nights that did it. I did see a couple after that that were obviously killed, but I thought maybe some would still develop. Since I don't see any yet, I'm afraid I'm not going to. :(