Answer: Pineapple Guava is self-fertile, but the pollen needs to be transferred from the male parts of the flowers to the female parts in order for fruit to set. Pollen is usually transferred by insects but it might also drop on its own, or be carried by wind. The weather needs to be clear and warm for pollination to take place. I suspect it was either too cold for insects to visit, or it was too wet (or the plant received overhead sprinkling during blossoming). You won't have fruit this time, but next time it blooms you may have better luck. I hope so!
Q&A Library Searching Tips