Hydrangeas flower from buds that form on new growth (new wood) from the previous season.  Any pruning should be done right after flowering occurs to avoid over pruning or removing the plants new wood and flower potential for the next season.  Also, often winter in the northeast can kill new wood again eliminating the plants flowering potential.  

If your hydrangeas failed to flower this year, let them regenerate new growth and protect them from the winter elements.  You should have flowers the following season.

To guarantee beautiful hydrangea flowers, Orsini Landscaping suggest using the Endless Summer Hydrangea.  Endless Summer is a perpetual-flowering big-leaf Hydrangea that blooms virtually all season long. And because Endless Summer can flower repeatedly on new wood (or new growth), you can be confident that regardless of whether the plant dies back to the crown or is trimmed at the wrong time, you'll still get wonderful flowers that grow all season.