Buds start to appear but then just fall off, what is the issue?
This is a complex answer, with many reasons for this to occur. The most common issue is that it did not receive at least 14 hours of darkness per day prior to setting buds. There are many other reasons, though. This article will help you: https://www.gardeningknowhow.com/ornamental/cacti-succulents/christmas-cactus/christmas-cactus-bud-drop.htm