I suspect this may have happened because the plant was not gradually transitioned to being outdoors in the sunshine. More information on successfully transitioning plants to outdoor life can be found in the following articles:
And, you may want to consider repotting your plant from the pot/soil it came with when you bought it. Some fresh, moist well-draining soil might do wonders for it along with a little fertilizer.
For more information on angeloina plants, please visit the following link: