All my saved customers have disappeared off the mobile app. They are still there on desktop.

Welcome to the Community, @paul218. I've got some information you need so you’ll be able to fix this issue with your QuickBooks Online App.

Let’s try to do some troubleshooting steps first to sort out this issue with your customers disappearing from your mobile app. 

First, let's uninstall and reinstall the app for a clean slate. You need not worry since it won't delete any of your app's transactions. Here’s how: 

1. Tap Settings on your phone.
2. Select Apps and Notifications, then locate the QBO app.
3. Hit Uninstall. 

From there, you can now reinstall the app.

Also, you can clear the apps’ data to help refresh the program. For more detailed steps, check out this guide here: See your latest data in the QuickBooks Online app.

Moreover, I've added articles about the different app features: 

• Overview of the mobile app
• Compare mobile app features

Please let me know if you need clarification about your QBO mobile app, or if there's anything else I can do for you. I'll be standing by for your response. Have a great day and stay safe.