A lace cap would be at the edge of its hardiness capabilities in zone 5, but I don't know why it flowered in the previous years unless they were just a few mild winters - has anything changed in the environment so that it now has less protection? If it is not leafing out right to the ends of the branches then the problem is that winter is killing the flower buds. So, first question is are the tips of the branches still alive? If they're not you aren't going to get flowers this year. There are some suggestions for how to winter protect them in future here:
http://www.hydrangea.com/Winte...
The other question is soil pH and whether you've fertilized and if so with what?
