Did your Plumeria lose all the leaves? Do not worry: this plant is very sensitive to the decrease in brightness. Therefore, in winter it enters a vegetative rest much more evident than many other plants: it is not so much a matter of cold (however low temperatures must be avoided) but of light itself; it is also necessary to avoid the cold air currents. What you need to do is to wet Plumeria much less in all winter months, keeping just a thread of moisture in the substrate, and not fertilize it. You will see that as soon as the days come to lengthen in spring, the stems will start to emit the new leaves and... you can take a big sigh of relief, enjoying fully your favorite plant.