Welcome to the Community. QuickBooks is designed to be an easy-to-use program. It's vital you're able to experience this benefit without running into issues. Rest assured, I'll be happy to help so you're on the right track.
In order to troubleshoot this issue, I recommend uninstalling and reinstalling the app. This is a good way to troubleshoot bugs that affect the app. By reinstalling it, this ensures you're on the latest version of the mobile app. You can visit these links to reinstall the QBO mobile app: