Why can I only see a small selection of my customers on the mobile app?

As per checking on my end, the customer's list in the QuickBooks Online (QBO) app is fully accessible, Davidtinker. Let's work together to fix the issue you're having.

Beforehand, may I know what you're trying to accomplish before navigating through your customers? Any additional information or a screenshot would help sort this out accordingly. However, if this issue happens when you're on your customer's list and can't see all of them, I'd recommend refreshing the app's data. It can help stimulate the app and its system.

For iOS devices:

1. Open your QuickBooks app.
2. Tap the Settings menu and press General.
3. Pick iPhone Storage. Then, choose the QuickBooks Online app.
4. Select Offload App to free up the app's data.

For Android devices:

1. Open your QuickBooks app.
2. Navigate to Menu ☰ and select More Options ⋮.
3. Press Settings and choose Refresh Data.
4. Confirm the action by tapping YES.

Nevertheless, if the issue persists, kindly follow the steps provided in the Fix other app-related issues section from this link to troubleshoot and resolve the issue: Fix common errors in the QuickBooks Online mobile app.

Finally, I'll include this article to give you a proper list of available features of QBO supported on your app that vary by device: Compare mobile app features.

I'll be here once you send updates on this thread or have follow-up questions if some of your customers are still not showing in the app or any other concerns in QBO. I'll make sure you're taken care of. Have a good one.