Hello yossi-h-s,
Glad to have you join the Community. QuickBooks is designed to be an easy-to-use program. It's important 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.
The app is also designed to show all your clients. In the event the app isn't functioning normally as you've described, 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:
Give this a try and feel free to keep me posted on how you make out. I'll be a message away.