Hello there, @Osmosis_pb. I can see the urgency of getting your QuickBooks Online (QBO) app issue fixed.

Let's update the QuickBooks mobile app and your iOS (iPhone) to their latest version so you can open and use QBO accordingly.

You may have an outdated version of the QBO app and iOS (the app needs iOS 12.2 or later to work properly). That's why you're unable to open and use the QuickBooks app. Updating them is necessary to help you access new features and fixes. 

First, update (you can also update apps manually on your Apple device) the QuickBooks mobile app. Here's how:

1. On your device, open the App Store.
2. Select the Today tab, then select your profile.
3. In the Available updates section, look for the QuickBooks mobile app.
4. Select Update.

Next, update the latest version of iOS. To do this, here's how:

1. Back up your device using iCloud or your computer.
2. Plug your device into a power source and connect to the internet with Wi-Fi.
3. Go to Settings, select General, then tap Software Update.
4. 1. If you see two available software update options, choose the one you want to install.
5. Tap Install Now. If you see Download and Install instead, tap it to download the update. Then, enter your passcode, then tap Install Now.

Once you're done, go ahead and open your QBO app. 

Also, you may want to check out this article as your reference to guide you about the QBO app features available on supported mobile devices: Compare mobile app features. It contains a comparison chart between Android and iOS devices.

Let me know if you have other concerns about opening and using the QBO app. I'm always ready to help. Take care, and have a great day, @Osmosis_pb.