Q.My Duranta Branches Are Black & Not Flowering
Duranta branches are black & not flowering.

Certified GKH Gardening Expert
This can be a sign of a few things. My first suspected thought would be soils that are too thick. This Will choke out the roots, which will cause rot. Another though would be chilly weather. They are hardy down, much, further in temperatures than you will receive, though.
This leaves two, main, suspects...
Infection from thick soils, or infection from insect infestation.
https://www.gardeningknowhow.com/ornamental/flowers/duranta/care-of-duranta-plants.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/yard-drainage-problems.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/what-is-well-drained-garden-soil.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides