Why won't my jelly set?

I wanted to make some jelly with stewed fruit in it. DS likes jelly but doesn't always eat his fruit. He loves those jelly cups but they get so expensive and I thought - yep, I'll make my own.

I stewed some apples and put them in with the jelly before it set.

Now 24 hours later - IT STILL HASN'T SET. I am guessing the water content of the fruit was just too much for the gelatine content of the packet jelly.

Would I be better off using fruit juice and powdered/leaf gelatine and stewed fruit?

Anyone have any recipes?

Thanks for your help.