missing step: after making the JABBA, make a world interaction upgrade and put it in the transfer node, it will mine the cobble pretty quickly. as of learning this and applying it in the machine about a minute ago, i already have 5x64 cobblestone. please include this step
If you don't have a source underneath it that can heat it, it isn't going to turn into lava. When u place the crucible on a torch it will heat up and melt the cobblestone. The heating source will set the speed of transforming, so a torch is 1x the speed, lava 2x the speed and so on.