Each time you launch the app? Are you launching it from an email message?
When launching the app from an email message, you must be logged in with the same email as the one receiving the notification.
If the problem persists I would suggest to reinstall the app.
What device are you using?
I have the same issue. Every time I launch it makes me log in. Not from an email message, just launching as per normal.
Try reinstalling the app from the app store and let me know if the problem persists.
Customer support service by UserEcho