I'd be happy to help you troubleshoot the error you're experiencing when checking customer balances in the QuickBooks Online (QBO) mobile app, @dsember.
To start, make sure that you're using the latest version of the QBO mobile app. If you are, try checking the balances again to see if the error has been resolved. If not, clearing the app cache can help. This will reset the app to its default state and can often fix issues like this.
To clear the app cache or data storage, follow these steps:
Open your phone's settings app.
Look for the QBO app.
Tap the clear data or the clear cache option.
Once you've done that, log back into your account and check the customer balances again.