I think it may be having a rest and will flower next year, but when you say 'mature' how old is your tree they are short lived 25-30 years. They are sun worshippers and need full sun to flower well. Mine flowers profusely (I have just put a photo of it flowering on my photos this week) but about 4 years ago it hardly flowered and I was advised to top dress it with Ericaceous compost once a year which I do. Its now between 10-12 years old.

thanks. I have no idea how old it is as I only moved in 2 years ago. I'll try top dressing it as you suggest

fingers crossed