If you find your jam didn’t set, it could be for a few reasons: the sugar wasn’t fully melted or your raspberries were extra juicy and that extra liquid affected the setting process. Make sure to give the jam the full 24 hours. If it still hasn’t set, stick it in the freezer and then let it thaw the next day. If it still hasn’t set, you can make another batch of the pectin and water and add the jam back into it and stir until everything is fully dissolved.