No trouble with notification sounds on my Note 2.... So, some things to check:
- With default settings, the app only notifies about new, unread messages (and won't notify about new read messages). This can be changed in the app's settings.
- Do you, by any chance, have a "night mode" or "weekend mode" configured in my app, which forces silent notifications? This is again in the app's settings, in Extended mode (top item).
- Is there a per-account silent notifications override? Long press the account, choose Special Settings to check