Hi Cara,
Here is some information previously shared by Linda Lou:
re: Gelling of jams, jellies, and preserves How to Remake Jelly that Didn't Thicken/Gel Happy Cooking!
Betsy
In reply to:
I just made a bunch of blueberry jam I followed the recpie on the liquid pectin package. I doubled it because I had so many blueberries. My jam is syrup, but I want jam. can I reboil and add more pectin?
cara, NH