I also get empty caerulea fruit. Occasionally there will be a ripe fruit that has very small undeveloped seeds but it's usually just full of air. I've never attempted to hand pollinate it but I have used the caerulea pollen on other passies.

I have the same plant, and all my fruits are orange, and have reddish/orange seeds inside but the fruits are hallow, withtout any flesh. These are non-edible fruits. Not an edible variety.

My caerulea fruits are completely empty, no arils, nothing, just air.

Passiflora caerulea is a very variable species that needs to be cross-pollinated from another plant to set fruit. I have grown many over the years and generally they are pretty full of seed - see link below.
The fruit are edible when orange and ripe but are not very tasty. In all Passiflora unusually it is the seeds with the arils around them that are the edible bit and there is no flesh as such. Just bits of pith.,
Myles

Here is a link that might be useful: Passiflora caerulea

As Myles said, caerulea aren't normally self-fertile. They need another, non-clonal caerulea nearby for pollination. I have a standard caerulea as well as a Constance Eliott, and get many, many, many seed-filled fruit. The inside of the orange fruit is filled with gorgeous, juicy, brick-red arils. The fruit from my standard caerulea is vile, so utterly bland as to be repulsive. My Constance Eliott, on the other hand, has mildly sweet pulp and is edible. It's not tasty enough for me to go out of my way to eat some--not with maypops on the other side of the yard--but it's interesting to see such diversity among a single species.

And as a data point, my foetida var. gossypiifolia produces hollow red fruit regularly, and needs a pollinator to produce pulp and seed.

That's so odd. My foetida also produces red fruit but it's full of juicy arils and viable seed without having a pollinator.