Certified GKH Gardening Expert
This can happen if it is exposed to temperatures below 50 degrees. It is not hardy at all to cold weather. This can also happen due to overwatering, or putting it in incorrect soil type. Usually it is the cold that does it though.
Here is an article for more information:https://www.gardeningknowhow.com/ornamental/cacti-succulents/christmas-cactus/christmas-cactus-cold.htm
Thank you so much. Can this branch re-grow? Would I put it in water or in rooting hormone?