On the QuickBooks app, my invoices are marked as not sent even though I have sent them and customers have received them. Just started doing it, never used to.

Let’s perform some basic troubleshooting steps to get you back on track, laurence4.

We can check to your QuickBooks Online (QBO) on the web if the sent invoices are marked as sent. If so, your mobile app data should always be in sync together with QBO on the web. We can change the data connection on your device. If you're connected to Wi-Fi, turn it off and use cellular data and vice versa. Then, open QuickBooks again and access the Sales menu. If you get the same result, close and restart the app. Then, refresh the app by going to your settings. Here's how: 

1. Tap the Menu button.
2. On the top-left corner of your screen, tap on the Gear icon.
3. Scroll down and select Refresh Data.
4. Press Yes when prompted.

Also, make sure you have the latest app version installed on your Android device. If you have an outdated version, uninstall and reinstall it to fix the invoice issue. Just download the app again from the Google Play Store. Here's an article you can refer to for more details about QuickBooks Online mobile app. This provides you with information on apps that are available for download. 

Feel free to go back to this post after performing the steps as I want to ensure this is resolved for you. Have a great day ahead.