Apple jelly failure

[beetiger]

I do not seem to be able to make apple jelly this year. I have tried to make several batches, and although one came out just fine, the rest haven't jelled and have just turned into hard-candy in a glass jar, of pretty much no value. Today's failed as well, but at least this time I've had the foresight to pour it on a silicon baking sheet and I'll hopefully have honey-apple-jasmine candy, in eadible pieces, not stuck in a glass jar.

But I'm really really confused. I've been doing this for years, and I've never had a batch fail before, and this is the fourth time. I must have forgotten something in the last two years, but I really can't figure out what.

I'm sad and confused by this.