I have 3 hydrangeas that only had about 2 flowers each this year. These face east and get full sun until about 2 pm in summer. Big, lots of green but no flowers. I put holly tone on in spring. These are into their 3rd year.
Few Flowers on Hydrangeas
Certified GKH Gardening Expert
This is likely a pruning issue. Some hydrangea varieties bloom on old wood (wood that grew the previous year during late summer and fall) and should be pruned in the summer before August, while others bloom on new wood (stems that grew that same spring and summer) and should be pruned in fall or winter.
Here are some other possibilities for why a plant wouldn't bloom: