Answer: If you are growing a bigleaf hydrangea (Hydrangea macrophylla), the most common reason(s) for lack of bloom are excessive winter damage and/or pruning at the wrong time. These bloom on old wood that grew the year before. If stems are killed back to the ground during the winter, or if the plant is pruned off in fall, winter, or spring, it will not bloom the next summer.
Additional causes for lack of bloom include too little sun (direct sun all morning should be sufficient) or lack of nutrients or lack of water. Since the plant has grown good foliage, it is probably not due to lack of light, nutrients or water.
If you have a peegee hydrangea (Hydrangea paniculata), it may be a matter of time in that this is a plant that does better as it matures. It might also prefer more sun and can handle sun all day long if the soil is evenly moist.
Since I am not sure which kind of hydrangea you have, you may also want to consult with your local county extension and/or local retailer for more advice. Good luck with your hydrangea.
Q&A Library Searching Tips