Did you leave your plant outside where it experienced cold weather (not necessarily freezing , just cold?)
Is the wood still green if you lightly scratch a bit of the bark off with your fingernail?
Many tropical shrubs can go dormant just like any temperate, deciduous shrubs. I actually keep a lot of tropical shrubs in my unheated garage over winter and they usually go dormant and drop their leaves at some point. In the spring, they re-flush. It is an easy way to overwinter them since the pests, like aphids and spider mites, aren't having parties in the foliage all winter long.
