If all other conditions (soil, watering, sun, air circulation, etc) are favourable for it to grow, it's mainly maturity.

I don't find them very easy to flower indoors. Even a very bright windowsill provides insufficient light. If not using grow lights, I would attempt to get them outside during the warmer months. That's about the only time mine flower - outside on "summer vacation" :-)

I keep them outdoors during summer. Many start growing inflorescence toward end of summer, and bloom indoors. They areunder lights whole winter, and many blooms last quite long time. Topsy Turvy always blooms (often multipe stalks), some may skip a years or 2 sometimes (for example, E. purpusorum bloomed last time 2 yrs ago). Here are 3, that started to grow inflo end of July (pic taken Sept. 1st) and are still blooming now: