How and when you prune your hydrangeas is crucial to whether it will bloom. Some hydrangea should be pruned right after blooming; others can be pruned late winter or early spring. A common mistake is to look at those bleached out old branches after leaf drop and assume they are dead. Big mistake. Next year's blooms may be in those dead-looking stalks. Here is more on pruning hydrangea: https://www.gardeningknowhow.com/ornamental/shrubs/hydrangea/prune-hydrangea-bushes-hydrangea-pruning-instructions.htm
If you don't know what type of hydrangea you have, don't prune for a year or tow and observe the plant's behavior: does is bloom on old wood (stalks formed the previous year) or does it bloom on current year's growth. Endless summer is a newish hydrangea that blooms on both old and new wood. It also requires more sunlight than older species.
Without photos and more information on growing conditions and your soil fertility and water management it is impossible to give specific recommendations. But as a general tip, nutrient deficiencies may be responsible. It is important to keep up with fertilization and compost mulching.