Perhaps it's been too long a day, but your store only has 4 items in it, however, when I went into the item itself, that the guy complained about, at the bottom it has a bunch of other stuff, like foodsavers, that appear to be running? Tis odd that they show up there and not in your store but anyway.
As a note, you can still recover from the negative if you satisfy whatever he wants and get him to do a mutual withdrawal. Having said this tho, depending on how mad he is it might go for naught, it you fix it and he doesn't do the withdrawal. Given he has other negs, it isn't as likely to work out.
I have recovered from a couple negatives by leaving the buyer a negative for not emailing or working with me to resolve issues they reported, then responding to them politely via email, and after discussing what they want fixed, fixing the thing they had issue with (which I would have done if they'd emailed me in the first place). Some folks don't expect sellers to work with them and neg off the bat without any communication. Usually if you're polite and offer to work with them they will come around.
Anyway in the worst case, looks like you're risking well under $50 to try to fix it up.
