Answer: Based on your description you are growing bigleaf hydrangeas. The most common reasons for lack of bloom are too little sunlight, incorrect pruning, and winter cold damage.
These hydrangeas need some direct sun in the morning or very bright dappled light all day to bloom well. In too much shade they may grow very lush foliage but no flowers.
The majority of these hydrangeas bloom only on old wood, meaning stems that grew the year before. If you prune the plant in fall, winter or spring you remove flowering wood. The only "good" time to prune is immediately after bloom.
If there is extensive winter damage, the flowering stems may be killed. Great care must be taken in the spring to be cautious and prune as little as possible, waiting to be certain the stems are dead before you remove them. Certainly, though, anything that is truly dead due to winter damage must be cut off.
Another cause for lack of bloom is late spring frosts that damage the buds.
I hope this helps you trouble shoot.
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