Hi, I've just picked some ripe (bright yellow) fruit from a friend's plant but they are empty! I had a passion flower plant a few years ago and the fruits used to contain a lot of seeds in a sort of jelly (a bit like frogspawn), Why are my friend's fruits 'hollow'?
while all passion flower fruit are edible, some are tastier than others...the decorative plants aren't bred for eating fruit so no one cares if they have juicy centres or not....like ornamental cherry trees having fruit that can be eaten but tastes horrible.
If its a choice variety, not just the boring blue and white, then the producer a) may not care whether it seeds, b) may not want it to seed as they want people to buy it not get it free. Seed doesn't always come true to the parent anyway. try layering a stem to propagate.