Why doesn't my elderberry jelly set up?

Elderberry jelly may not set up due to insufficient pectin, which is necessary for thickening. If the fruit wasn't ripe enough or if you didn't use a recipe that includes added pectin, this can also affect the jelly's consistency. Additionally, not cooking the mixture long enough or not allowing it to cool properly before storing can prevent it from setting. Consider re-cooking the jelly with added pectin to achieve the desired consistency.