There could be several reasons, but if you've followed the recipe exactly it's likely due to the mixture not boiling enough prior to placing it in the jars. You'll also need to place the jar in the fridge for a minimum of 4 hours to allow it to properly set and finish thickening.u003cbr/u003eu003cbr/u003eIf this happens there's no need to toss it. You can still use the jelly as a marinade or glaze.