I think the Benzoate might be a problem. I've never tried to ferment
anything that included it as an ingredient, but most sources indicate
that it will prevent fermentation. As an example, the following is from
a recipe on Jack Keller's web site:

"A second complaint was that at least two people had trouble getting
the must to begin fermentation. That problem, it turns out, was due to
the products being heavily preserved with additives. If the additive is
sulfite, we can solve it easy enough with a yeast starter solution and
adding the syrup to it bit by bit, but if the problem is potassium
sorbate or benzoate it will not ferment. Period. Read the labels
carefully."

Regards,

Greg