Might not be ruined, but probably will be a difficult ferment. First, what does the potassium sorbate do? It acts as birth control for yeast, keeps it from budding and reproducing.
So what you have to do is add lots more yeast than normal. I would start making a really, really large starter with something like three or four packages of the same yeast, let it go overnight. Then add. It will probably ferment for a day or two just fine, repeat the yeast starter as required.