Answer: It sounds like you have been taking good care of your plant, but Passiflora, the Passion Flower, is a perennial plant that should flower year after year. Perhaps it is just now gaining sufficient strength to bloom, but it may also be that it needs to be trimmed back hard in the spring to produce more blooming wood. Here are general care instructions in case you are missing something: Place in the sunniest spot possible and keep the soil moist except in winter, when only occasional watering is necessary. This is a tropical plant and as such prefers a long hot summer season outdoors; mist it if the weather is dry and be sure to give it plenty of water while it is actively growing.
To avoid shock, gradually introduce it to its indoor home (the reverse of hardening off plants to the outdoors in spring), since plants grown outdoors do need to adjust to the air/humidity changes. Since it is tropical, it enjoys winter temperatures no lower than about 55F at night, and temps somewhat warmer during the day. High humidity and good air circulation also favor its performance. Keep soil drier and do not fertilize during the winter. When spring rolls back around you can increase watering and resume fertilizing, and gradually reintroduce it to the outside, again to avoid shock.
And here is the important point: trim it back hard in the spring so it produces more blooming wood. You might also try using a fertilizer intended for blooming plants (with a higher middle number) as an excess of nitrogen can cause excess foliar growth at the expense of blooms. Let's hope it blooms this time!
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