Have you pruned the Hydrangea, Did you prune the hydrangea at the back end taking off the flower buds, hydrangeas [mopheads] dont need pruning really, only ocaisionally taking out old stems, or for really large hydrageas you can adopt renovation pruning by taking it right back if so you have to wait a year for it to bloom the following season, leave old flower heads on for winter protection and as a rule i nip them off mid april time.

That's two more than mine has Patsy!