Mourning my Sambucus 'Sutherland Gold'

Please help. I had a beautiful Sambucus 'Sutherland Gold' which was only about 5 years old and was quite big. It was the best thing in my garden, the jewel in the crown. This year, however, it started to bud....then nothing!  All the buds withered and died, some tried to form little leaves but got no further. I think it just died!  I've cut it right back to see what happens but I fear I have lost it. However, I have a smaller one almost next to this which is absolutely fine! What could possibly have happened to my big plant?? I would be so grateful to know.