It might be going dormant. What I have done in times past was to give it the opportunity for a fresh start next year by cutting it down as close to the ground as possible then see what it does next year. At my location there has been nothing but high heat and no rain for a month. The trees and bushes have begun leaf drop to conserve water and lawns including golf courses are scorched.

Is it pot bound? it could just be starving. Have you fed it recently?

don't do anything drastic until next year are remove 1/3 [evenly] from the shrub down to about 6". [renovative pruning] then the year after another 1/3 nd again the following year. this may give it the kick it needs to recover.

It's in the ground Steragram, its been there for around 15yrs, I did cut it right down last year at the right time to buds near the base of the plant :o))

Last resort - perhaps a phosphate feed (eg tomato fertilizer) early in the season might help another year? Or, and this might sound silly, threaten it that if it doesn't flower next year you will dig it out.. I had a plant apparently respond well to this threat some years ago. lol...

The flowers weren't as big this year, I would dig it out if I wasn't moving, that will hopefully be in about a years time,
plus I don't think my Husband & I could do this sort of digging anymore as the years are catching up with us, hubby needs a knee replacement & I have hip problem Grrr! Not fair, so much I would love to get on with LOL.

Thanks for all the info Guys & Girls xx