Journal is a part of Know Me Toolbox Plus, so you must have an active subscription to view or write in your Journal.
Also, Journal requires an active Internet connection. Even if you are currently subscribed to Know Me Toolbox Plus, your Journal entries won't load if your device is in Airplane Mode or can't connect to the Internet. Try connecting to a WiFi network or finding an area with better cellular service, and going back to your Journal again.
Don't worry, even if you can't see them for either of the reasons above, they're still there.