I have some plumeria that are fully leafed out, some that are just starting, and some that still look sleepy like yours. Different varieties have different wake up calls. First thing, stop watering. Do not water until you see the first full set of leaves or you risk rotting the cutting. As long as the cutting stays firm, you are ok. Just stop watering for now. The warm soil temperature is what helps them leaf out. Make sure you acclimate your little tree to warmer temperatures and 6 hours of sunlight, perhaps outside? They would love your humidity! You have drainage holes at the bottom of the pot? They love well-drained soil and do not like to be left in soggy bottoms so it has to drain out. Keep us up to date about your tree.
