I bought some Del Valle guava nectar yesterday and I'm trying to make
some wine from them. Overnight didn't spur any activity in my airlock
at all, when I would have expected ever so slightly a start. I should
probably wait longer, but I want to cover my tracks and know when I
might give up.

The ingredients were water, nectar, sugar and/or high fructose corn
syrup, citric acid/absorbic acid. I hear absorbic acid is a bane to
yeast. Is this true? If so, will I be able to work around it?

I gave my batches more yeast. If I don't have any activity by tomorrow
evening, I'll try a started from dry yeast; that way I'll know the yeast
was at least good when I pitched it.