If it were my plant, I'd stick it out in the sun. The only thing that's gonna fix that plant's problems is photosynthesis. It's probably working on bulking up it's root system now that it's in a bigger pot. Once it's happy with the size of its root system, it should start to take off, as Spicy Mushroom said.
   It's been my experience that Caribbean reds are resilient, vigorous plants. Give it all the sunlight it can stand (keep an eye on it for wilting, if it's not used to lots of sun), and let it do it's thing. If it pulls through, cool. If not… well, there are always runts that just won't make it no matter what we, as gardeners, do or wish for.