Sorbet contain ice crystals
A few possibilities, hard to say given the amount of detail:


you didn't blend the mixture smooth enough, so you have ice crystals from the water in small pieces of fruit that were left
you didn't churn it long enough, so when it finished freezing in the freezer, it developed larger ice crystals, while if it'd been churned longer they'd have been smaller
your recipe has too little sugar (too much fruit/water, including what was in the syrup), so it was never going to work out


See also What determines whether a sherbet will set or not? and Is there a magic ingredient that keeps ice-cream soft?, among many other past questions on soft sorbet/sherbet/ice cream.