How long has the star been imobile, how long have you had it and how was it originally acclimated? Any sign of color loss?
A star not moving isn't too big a concern as long as their general appearance is normal. Once they find a food source to their liking, they can stay put for days at a time. Chocolate stars are one that requires feeding unlike it's decorative couterparts. Small meaty seafoods placed underneath it will often accomodate their larger appetites.
Cheers
Steve