What size of pot is your Christmas Rose in? These are deep rooted plants so unless it is in a very large pot it is likely to be less than happy. Best planted in the ground.

I agree with Mg, especially if that pot is heating up during these dog days of summer. Roots must be kept cool, shaded & moist - like deep in the ground.

also check the roots for vine weevil. That can cause the plant to wilt.
have you had the plant standing in water for some time? that may make a plant wilt too.
Welcome to GoY too :o)