Answer: The most common reasons for lack of bloom on bigleaf hydrangeas are excessively cold winters, and/or pruning at the wrong time.
In your area (your zip code places you in USDA winter hardiness zone 5A, the coldest part of zone 5), winters are too cold to expect reliable bloom on these hydrangeas. The reason is that they bloom on old stems that grew the previous year. If winter kills back the plant, the blooming wood is lost. For the same reason, pruning in spring will remove flowering wood.
These do best in a sheltered location with protection from winter winds, and may need special winter protection as well. Some gardeners will encircle the plant with wire mesh and fill it with a nonpacking insulating material such as dry straw or oak leaves. Cover the top with plastic tarp to keep it dry inside but do not enclose it completely, you do not want to have condensation inside it. This is put in place in late fall and removed in the spring.
Another possibility is that spring frosts are damaging the buds, if there is frost after it has begun to grow you would need to cover it and protect it from the frost.
There are some bigleaf hydrangeas that are able to bloom on both old and new growth and might do better in your climate, such as Endless Summer. You might try one of these with better success. I hope this helps you trouble shoot.
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