Thanks for asking the Apple Support Communities for help redownloading your purchases. Please ensure you have tried all the steps provided in the following help article:
Redownload music, movies, TV shows, apps, and books from the iTunes Store, iBooks Store, and App Store
If you still have issues, don't hesitate to let us know. Please inform us what you are seeing, any alerts or errors, or what is actually happening when it doesn't allow you to redownload your purchases. Thanks and have a great evening.