Did you prune your hydrangea? You may have pruned off potential flower buds! Avoid pruning any reblooming hydrangeas or hydrangeas that bloom on old wood. That includes: Big leaf, mountain, oakleaf and climbing hydrangeas. (Panicle and smooth hydrangeas bloom on new wood/growth and can be pruned early in spring if necessary.)
Your hydrangea may have suffered harsh winter damage, even if it was an established plant. Do you only see growth at the bottom of the plant, with a lot of dead branches sticking out? It is likely that those branches are dead.
If you have a deer problem, they may have eaten the buds flower buds (if not more!) off of your plant.