Check the Google Assistant account you are using on device, sometimes if you're using more then 1 google account on same device it consider the default account so you have to select that developer account manually. You can also check if your shortcut is available for your device by open Google Assistant settings and search for 'Shortcuts' section and you'll find your App there and after that you can even create a short keyword to use your OPEN_APP_FEATURE like "Hey Google, Emergency"