I have been canning for years with no problem with my jams jelling.
I saw Bernardin while picking up my supplies for my jams. Bernardin was cheaper that should have been my red flag. But opted to try the brand as I use Bernardin products for years but always used Certo for jams and jellies.
Both batches that I used Bernardin didn't jell and had to redo. I wrote to Bernardin about my problem.
Well not a word back, didn't expect anything except a return message saying how sorry they were for my extra work. NOTHING.
So back to Certo and success.