Answer: Unfortunately, I am not familiar with a "Silver Blue" variety of hydrangea, however if the flowers are supposed to be in the blue range I would expect it to be either a Hydrangea macrophylla or H. serrata variety.
These plants usually fail to bloom for one or two reasons, both related to the fact that these plants bloom on the previous year's growth. The first is winter damage or late spring frosts kill the tips of the branches where the flower buds are; the other is that incorrectly timed pruning (fall or early spring prior to bloom) removes the buds. The only time these plants should be pruned is immediately after they bloom -- apart from removing dead or severely damaged branches which can be done any time. If you are looking at pruning winter damage, be patient and make sure the branch is truly dead before you remove it.
Also, severe winterkill would indicate that the plant is not sited in a protected enough location. A site sheltered from wind can be helpful in reducing winter damage.
You would also of course want to make sure the variety is rated hardy for your zone. I hope this helps you trouble shoot.
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