Den. kingianum needs a dry and cool winter rest to bloom, also it needs very bright light during the winter.
If you grow it indoors under lights, I think that is the reason it doesn't bloom for you. Might not get enough light and the temp propably stays to high.
It's also wise to withhold fertilizers from about now until spring.
I think you might find
this worth reading.
Mine are currently outdoors and I bring them in when night temps get lower than 41 F for several days in a row. When I bring them in, they go in a 'cold' room with a South faced window, where the window is open 24/7, even during nights with frost - until I'm sure the new growths are buds. That's when I start watering again (light waterings!) and allow the day temps to get a bit higher.
Nicole