Why is QuickBooks app not displaying properly? Why Can not switch between customers to record payments as no back button displays.

I can see the convenience of switching between customers to record payments through the QuickBooks Online (QBO) mobile app, @b2smom. That's why I'll make sure you're able to utilize the back button again to effectively handle your everyday business transactions.

The QBO mobile app stores cache to speed up your experience in performing your tasks. Once it's full of cache, you'll experience some display errors from the system. You can clear your app data to refresh the system and remove the older files that cause the unusual behavior. 

For iOS devices, here's how:

1. Go to the Menu icon at the top left corner of the screen.
2. Choose Help & Feedback.
3. Select Refresh Data and Refresh.

In case the issue persists, I'd recommend uninstalling (tap and hold the app icon) and reinstalling the app. This is to ensure the version you'll be using is updated. 

I'm also adding this article to learn more about the QBO app features available on supported mobile devices: Compare mobile app features. It contains a comparison chart between Android and iOS devices.

Let me know in the comments below how it goes. If you have other concerns about the QBO app, I'll be right here to help. Keep safe, and I wish you continued success, @b2smom.