These vines are really picky about their environment. It's not an easy plant to grow. I agree with FataMorgana it could be any of those things. What are your growing conditions?

Temps dip below 50F. Perhaps low humidity. Missouri Botanical Garden says seldom sets fruit indoors. Several posts on Garden Web (2006 thru 2013) from folks who say they're successful live in central Florida.

I always reuse my potting mix and this year I have passion vines coming up in everything. You see an empty pot sitting around for months and figure there's nothing in it.....wrong. lol I know loads of folks that like okra. I'm just not one of them. The slimy texture gets me every time. Piper nigrum is pretty easy to root. I don't have any now but you might want to post on the exchange and see if anyone can send you some.

I checked my records but unfortunately I was a bit slack with this one. My guess is about 4 years old. Bought it as a small plant and then left it in its pot at the base of a tree. Ended up forgetting about it until it started to spread out across the ground and up into the tree. Used the stem on the ground as a cutting for a new plant. They do grow easily from cuttings. The pot was sitting on a brick but the roots still went down into the ground. Got 3 plants now, really like the look of them so it doesn't matter about the fruiting.