Was it pruned last year? That is often the cause of poor flowering. They produce flowers next year on wood produced this year.
Otherwise feed with high potash feed.

Sometimes the buds freeze if you have a very bad winter. Last year my gardener gave mine a trim...and cut off all the flower buds! If you use a high nitrogen fertilizer, that could promote foliage over flower buds. Hydrangeas need lots of water - it's their name. Any of these could be reasons for no flowers.

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this is excellent advice an pruning John.

Just wondering if you have been feeding it with a general fertilizer with high nitrogen as the leaves looks so lush and healthy. . I too would leave off the general feed for a while and use something like tomato fertilizer or a scattering of sulphate of potash. If you have access to fresh seaweed I've found it works brilliantly with hydrangeas. As long as you wash the salt off first you can just lay it on the soil around the plant. It does have nitrogen in it but lots of other beneficial elements too including potash.