Answer: The most common reasons for lack of bloom on bigleaf hydrangeas are pruning at the wrong time and winter damage, plus occasionally spring frost damage.
Your zip code places you in winter hardiness zone 6A, which depending on your microclimate, might actually be as cold as zone 5. This is very cold for this plant. This plant blooms on old wood that grew the year before. If winter kills back the stems, there will be reduced or no flowering the following summer.
Also, pruning can remove flowering wood. The only "safe" time to prune these is in summer right after bloom. In the spring, be very patient before pruning off any stems that appear to be winterkilled, sometimes they look unpromising but are still alive.
You may want to try providing a wind break for the plant, or possibly insulating it. To do that, place a cylinder of wire mesh around the plant and fill it with nonpacking material such as straw or oak leaves. Cover the top with a bit of plastic or tarp to help it stay dry, but do not enclose it completely (you do not want condensation to occur inside the cylinder.) Some gardeners also wrap it with burlap. Put this in place in late fall after the plant is dormant, and remove it in early spring. In the spring, cover the plant if a frost is expected after the buds begin to swell. I hope this helps!
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