Let's reset your app to clear your QuickBooks app cache. This will help delete your app's history and cookies and fixes any issues. Let me guide you how.
Once done, try accessing your app again.
If you're getting the same results, you'll want uninstall and re-install the app.
To download, please click this link: QuickBooks Mobile App.
Please visit our page about apps for QuickBooks Online in case you need some help articles for your future tasks.
Let me know if there's anything else you need help with.