Too bad you didn't ask here how to defeat sorbated cider. Or if you did, I apologize I didn't see it.
Sorbate stops the replication of yeast, but doesn't interfere with the fermentation. So what you needed to do is create a huge yeast starter. I have done it in the past by making a Graf, starting the wort fermenting a couple days before adding the cider. If you don't like graf, then I suppose you could do it by getting a cheapo nontreated apple juice and making a starter with that.