Failing to make mozzarella
The problem is the organic milk. Or rather, the fact that organic milk available in grocery stores is high-temperature pasteurized, rather than conventionally pasteurized. That helps it keep a lot longer, but it disrupts the proteins so that they don't coagulate well enough for cheese.

I'm told that there are brands of conventionally-pasteurized organic milk, but I've never seen one. You might try it with plain old grocery store milk, and it should work. Or you could try to find a local producer, who won't use HTST pasteurization. (You might even be able to find unpasteurized milk, though the USDA definitely frowns on that: even though you're cooking it you won't have aged the cheese long enough.)