The Hydrangeas that bloom on old wood are from the macrophylla family. These include Nikko Blue, Endless Summer and many other pinks and blues. When I say they bloom on old wood I mean that they are busy right now setting buds for next summer. So next year when they take off growing in the spring, the flower shoots will actually emerge from the older wood, the wood that was produced this year.
The hydrangeas that bloom on new wood are typically the white hydrangeas like Annabelle and Paniculata Grandiflora (PG). They put on new growth in the spring and then later in the summer the new blooms are actually produced right at the end of that new growth. That’s why the Annabelle and PG are such prolific bloomers. They set flower buds and almost immediately those buds produce big, beautiful, abundant flowers. Almost nothing can go wrong with their blooming sequence.
But with the Blue and Pink Hydrangeas (macrophyllas) all kinds of things can go wrong with the flower buds. Since the flower buds are produced in August and September they have to make it through the harsh winter before they can bloom. The flower buds can be damaged by extreme cold.
Pruning? You should prune macrophylla hydrangeas right after they bloom, before they have a chance to start making new flower buds. Annabelle and PG hydrangea and other hydrangeas that flower on new wood can be pruned during the late fall, winter or early spring. Once they start growing in the spring, do not do any pruning until after they bloom.
One of the most popular new varieties on the market is “Endless Summer Hydrangea” and it is known to bloom more than once in a season. It’s in the macrophylla family and sets flower buds on old wood, but it is also known to set more buds and produce flowers during the growing season. It should still be treated as a hydrangea that blooms on old wood.
So… with all of that said, if your hydrangea did not bloom then the flower buds might have gotten pruned off, or more likely the buds were damaged over the winter.