If you've recently updated to iOS 8 and are having trouble sharing your Napster content on Twitter, try disconnecting and reconnecting your accounts:
1. Open the Settings on your phone and then tap Twitter
2. Tap your Twitter handle > Delete Account
3. Then Enter your Twitter username and password and press signed in
4. Close out Napster app and try again.
Note: People connected to multiple Twitter accounts will need to remove all of them from their phone settings before reconnecting their Twitter accounts.