Grow rocks? Get a new hobby? No, I'm just kidding.

What kind of hydrangea is it? Macrophylla, Arborescens, Paniculata, Quercifolia? Some types should not be pruned in spring (macrophylla and quercifolia) but if pruned then shortly after they bloom. Being in zone 4 you probably aren't growing macrophylla? Macrophylla had winter kill all over the eastern part of the US so they won't put on much of a show this year.

You can also kill the invisible flower buds of the other hydrangeas if you time your pruning "right"... after the flower buds have developed in Spring but before they become visible and open.

Macs and oakleaf (quercifolia) hydrangeas are not hardy to Zone 4 so I would think you probably have arborescens or paniculatas. Pruning could have affected them. But also consider that, in your zone, paniculatas will bloom in July-ish so maybe you will get blooms later on.

By the way, paniculatas have panicle-shaped blooms or pyramidal blooms. Arborescens will have white mophead or lacecap blooms.