In your zone you would have to winter protect this type of hydrangea and even if you did protect it, this past winter caused havoc in most regions of the country with macrophyllas.

This is supposed to be a late flowering mophead so I would regularly expect blooms to be late (as in June or early July). Flower buds develop always after bloom in July-August. Transplanting it -for example, in the Winter Months or Spring- could have killed the invisible flower buds.

However, a more likely problem is the winter hardiness. It can bloom unprotected in Zones 6 and higher but in Zone 5, you need to winter protect.

Make sure you also do not prune it. Best time to prune is after it has bloomed but before July-August. Keep your fertilizer regimen light as too much can produce a nice shrub with green leaves only.