I've never tried, but I have a pepper vine. It doesn't do well here because it's too cold at 1500 ft elevation, prefers sea level (does OK in my greenhouse, but then it takes over). Maybe you need to keep the seeds warmer?

I live in the Florida keys and I've tried to keep them as warm as I possibly, I leave them in full sun for at least 8 hours..

I think i need to get my hands on some super fresh seeds too like right off the plant.. That would probably help.

I've never tried the seeds, anyone who has them just says to use cuttings. I've got a lot of them running around, up and between trees. They like to explore.