What species/hybrid is it? How much sun does it get? What color are the leaves (shade of green, any yellow in them)? Does the parent plant bloom regularly?

There are a whole lot more questions that I'm not thinking of. Any details you have might be helpful, even if they seem irrelevant.

A picture is worth a thousand words...

WITHOUT FERTILIZER!!! may be the problem. Try a fert. with more P and K than N or a bloom booster. This is just MHO and I'm not that familiar with passies but it works well for other plants.

taz,

I just got a plant (P. umbilicata) from Grassy Knoll and along with the plant came growing instructions. She says "Fertilizing plants in the ground is probably not necessary". I'm not sure I agree, but Elizabeth certainly knows her stuff. From what I remember commercial growers of P. edulis fertilize pretty heavily--and those are people whose livelihood depends on the plant blooming.

I do wonder about light, and the reason I ask about leaf color is that if the leaf is chlorotic (yellow regions in addition to the normal green) that may indicate nutritional deficiencies (nitrogen, iron). It could also be a sign of spider mites, which also wouldn't be so good for flowering.

Well he said it was growing good which could just be due to nitrogen and also no flowers could be due to it just getting nitrogen. God I hate spidermites. They infested my entire tomato crop indoors. I took cuttings and dipped them in double strength malathion then planted the cuttings in the garden and had to battle them all year. The colder weather is what really stopped them from doing so much damage.
Yes a macro or micro would help to see any critters and just a picture of the leaves could help us determine if it has a deficiency. A soil test from lowes might tell us something also. I think they run about $10

He might try adding some potassium. I heard a while back that it helps with blooming. I add a small amount of chopped banana peels to the soil in my container passies. It seems to help but I don't know if that's due to the potassium or the breakdown of organic matter. I use a bloom booster during the growing season for my mature plants. I've also been adding CalMag Plus a few times a month either as a foliar spray or root feed for the past couple months because I was getting a lot of chlorotic foliage.