Of course I don't really know but this will be my guess. You got hit with some warm weather early on, your shrubs broke dormancy, and got hit with a freeze again, killing off the unfurled buds. Do you remember them starting to leaf out early?
How many years do you have them?

Hi Loretta, Thanks for the reply. The plants are 5 to 10 years old. I think you might be on to something. Although I was in Florida and unable to observe the plants, your theory is very plausable since we had a number of 60 degree days last winter. Thanks again.

My old, regular, no-name hydrangeas are in wonderful shape. My Lemon Wave Hydrangea, planted 3 years ago, died back as did a neighbor's. Her's is in a really protected spot. We didn't really have any late frost, which I think would kill the flower buds, but not the entire branch. My theory is that the drought of last year and this spring hit them hard. At least they are sprouting from the roots, and I will try to water them more this year.

The same thing happened to mine. I was so upset but happy to see new growth. SO, I shouldn't expect flowers this year?
I thought it was because of the drought last summer in NJ.

Cold and drought will cause tip dieback of course but in the future, watch your hydrangeas during winter. You will see that during winters where the weather fluctuates and winters get too warm, your H. macs will unfurl the first leaves from the buds fairly quickly starting from the bud closest to the tip. If the weather stays warm, the next set unfurls and so on. If it gets too cold after that, the bud dies. The whole stem may not die and may still bud out further down the stem. I still get some flowers on these stems. But sometimes it starts over from the ground.