Hydrangea Non Flowering ?

My friend at work has a Hydrangea bush , type not known . This used to flower OK . Now it just grows long stems and does not flower. What can he do to get it back on track ?

TIA

 

pruning and feeding comes to mind as depending on the variety if he prunes too early he can cut all the blooms off for this year if its a early one , but what type is it ?? , if he has had it a while ? what's changed , getting crowded out ? less sunshine ?

Spruce