Don't prune hydrangeas.

Most hydrangeas bloom on last year's wood, so if it dies during the winter (because it was cold) or if you prune it off, it will not bloom.

Endless summer will bloom on both this years and last years wood, but if you prune it before it blooms, it won't bloom either.

Sometimes they often take until fall to bloom depending on climate, in Kansas city it shouldn't take so long, but maybe you're in a cold microclimate.

I have some hydrangeas that NEVER bloom (including Nikko blue) because they're not that cold hardy here in Michigan, but my Endless Summers are reliable bloomers for me.

The only pruning I would do is on dead wood, but Hydrangeas are slow starters so wait until mid june and if there are any stems or ends that seem dead, prune those dead bits. Otherwise, don't prune.

Then, to help it survive during the winter if it still doesn't bloom, build a wire cage around it with chicken fence, and fill with leaves or other loose fill material, and wrap with burlap. I don't think you need to do all that where you live, but some people have to do that so maybe you do too.