I made 8 pints of concord grape jelly and it's still syrup after 4 days. I used 3.5 pounds of grapes to make 4 cups of grape juice. I stirred in 6 cups of sugar and brought the mixture to a boil and then added 6 oz of liquid pectin and boiled hard for 1 minute before filling the jars. I then put them in a hot bath of boiling water for 5 minutes. Any ideas why the jelly hasn't jelled? IS there a way for me to re process it?