Thanks for writing. There are lots of reasons hydrangeas may not bloom, including:
Pruning at the wrong time of year
Growing them in too much shade
Fertilizing them too much
Growing a type that's not appropriate for your climate
Without knowing what types you have and what conditions you're growing them in, I'm sorry, but I can't say for sure why yours aren't blooming. I hope that one of these common causes sounds right for your situation!
---Justin, Senior Garden Editor, BHG.com