Betsy, a sebae anemone is one of the most delicate, if not the most delicate of the commonly available anemonies. They need a very mature tank with good lighting, good flow and excellent water parameters.
How long has your tank been running?
How much live rock?
What kind of lights?
What do you have for flow?
What are your water parameters, specifically pH (after the lights have been on for a few hrs), nitrate, alkalinity and calcium?
Do you have a skimmer, and what kind?