I'm a real newbie at this stuff, but I have had a similar experience
with a grapefruit wine recipe. I think it is because i bought jarred
grapefruit that had sodium benzoate preservitive vs a can that had been
pasteurized. I'm doing a parrallel with a fresh fruit recipe and it is
merrily bubbling away. Just a hypothesis from someone who is learning.
Check your concentrate can and see what's in it.

Rick