The reasons may vary why your jam didn’t set up properly. It might have needed more cooking time. The acid in lemon helps the jam to have its gel texture.u003cbr/u003eu003cbr/u003eIf you followed the recipe carefully but it still didn’t set up properly, let the jam sit overnight in the fridge. If that step still doesn’t help to stiffen up and set. You might need to try re-cooking it for a bit longer.