If the yeast doesn't bloom, it means that the yeast has expired or the milk was too hot, killing it. If the yeast has expired, you will have to buy a new packet, and if the milk is too hot, then you can bloom the yeast again in less warm milk. Adding sugar is essential to feed the yeast and help it grow. If the yeast hasn't bloomed, do not use it in the recipe; it will spoil the entire recipe.