Quickbooks mobile only shows my customers through the letter M, how do I fix this?

Hi there, @capahalandscapin. 

Thanks for visiting the Community. QuickBooks collect cache to save you time when loading repetitive data and images. 

It could be that your apps need some updates. We can perform some application troubleshooting steps to view all your customers. Let’s start by resetting the data on your mobile application.

For Andriod, here's how:

1. From the More Options ⋮.
2. Select Settings.
3. Tick Refresh Data, then choose Yes.

For IOS:

1. From the Menu button.
2. Select Help & Feedback. 
3. Click Refresh Data, and then select Refresh.

Once done, log back in and check if you’re seeing all your customers. If it doesn’t work, I suggest uninstalling and reinstalling the app to refresh it. 

For future reference, you can check out QuickBooks Articles in case you'll need some easy steps with specific tasks such as sales and customer management.

Let me know in the comments below if you have any other concerns.