Why does my Passionfruit vine have fruit but it shrivels up and falls off before the fruit ripens

Passionfruit can be tricky to grow at times. This may be natural fruit drop as if the vine sets more fruit than is can support it will drop the fruit without ripening it. Also make sure it is receiving enough fertiliser and water as they are heavy feeders and drinkers. Try using Thrive Natural Pelletised Plant Food For Fruit and Citrus during the growing seasons, Spring Summer and Autumn.