Thanks for reaching out to the Community for support and letting us know that you're using an Android device. I understand how frustrating it can be when your customer list is no longer visible using our QuickBooks online mobile app. Rest assured, we will get that list working with just a few easy steps.
I recommend refreshing the app's data. Refreshing the app data plays the same role as clearing the cache from your web browser. Both collect cache to save time when loading repetitive data and images. These files can often become outdated or corrupted, causing issues like the one with your app not showing your customer list. I've included the steps below to clear the app's cache.
Select the menu at the top right and choose Settings.
Choose Refresh Data.
That's all there is to it. Once you've refreshed the data, close the app and reopen it for the changes to take effect.
I'm also including a few articles that you may find beneficial for the future below.