The most common reason for a hydrangea not blooming is that you have big leaf Hydrangea macrophylla, a  more tender variety and the flower buds are destroyed in the spring with cold weather. These are the most common mop head hydrangea that grandma grew. If so, you need to plant the more cold tolerant Hydrangea  paniculata or Pee Gee hydrangea or  one of the new mountain hydrangeas (Hydrangea serrulata) for cold climates. The "Endless Summer" Hydrangea is also good as it will make new buds if the spring buds are destroyed by a frost. The other reason hydrangeas do not bloom is lack of light. They like protection from the hot afternoon sun but do best with at least half a day of sun. Some of the hardier hydrangea paniculata varieties like full sun. Be sure to mulch the soil and water during dry times as hydrangeas love moist soil. Keep growing, Marianne Binetti