My first attempt at making cheese just failed miserably. Followed the directions to the “T” on a standard Mozzarella recipe and it just didn’t firm up after adding the rennet. The recipe called for ½ tab, and when that didn’t work after several hours (recipe said it would firm up after 1 hour), I tried to salvage by adding another ½ tab. Still ended up with a sloppy mess rather than something I could cut into cubes before draining. What went wrong?