In a window with morning light. Temp 80. Light solution of miracle grow when watered.
Why Is Easter Cactus Shedding Branches
Certified GKH Gardening Expert
Check the watering. Soil should be lightly moist but dry out between watering.
Also they do like cooler conditions.
To much fertilizer will also cause the plant to drop leaves. You need to fertilize only after the plant is done blooming, once a month.
Here is a link to refresh you on the care requirements.