Thanks for writing. Some common reasons why hydrangeas don't bloom are:
They get too much shade
They're pruned at the wrong time of year
Especially cold winter temperatures kill their flower buds
Their flower buds get zapped by a late-spring frost
They get too much fertilizer (and respond by putting all of their growth to leaves instead of blooms)
Do any of these sound like they might be a possibility? Keep in mind that different varieties have differing hardiness levels and light needs.
---Justin, Senior Garden Editor, BHG.com