I added potassium sorbate to my wine, but it is still bubbling. Whats wrong?
Nothing, really. While stabilizers such as sorbate, sulphites, and campden will prevent yeast from starting up (refermentation), they will not stop an activer ferment. Your best bet is to let the yeast run its course, siphon the wine off the sediment into a clean and sterilized secondary, and treat with the sorbate in the new container. After treating, let sit for a couple of days to see if any refermentation is taking place. If not, sweeten to taste and bottle. If it starts working again, repeat the procedure.