To resolve the issue with the Oxygen Advantage app not working and displaying an error message, follow these steps:

1. Restart the App: Close the Oxygen Advantage app completely and then reopen it. On iOS, you can do this by swiping up from the bottom of the screen and finding the app, then swiping it off the screen.

2. Check for Updates: Ensure that your app is updated to the latest version. Open the App Store, go to the "Updates" section, and check if there’s an update available for the Oxygen Advantage app. If there is, download and install it.

3. Restart Your Device: Sometimes issues can be resolved by simply restarting your iPhone. Hold down the power button, slide to power off, and then turn it back on after a few moments.

4. Check Internet Connection: Make sure your device is connected to a stable Wi-Fi network or has cellular data enabled. If the connection is weak or intermittent, it can affect app performance.

5. Reinstall the App: If the problem persists, consider deleting the app and reinstalling it. Press and hold the app icon until it jiggles, then tap the 'X' to delete it. After that, go to the App Store to download it again.

6. Check App Permissions: Ensure the app has the necessary permissions enabled in your device settings. Go to Settings > Oxygen Advantage and check if all required permissions are granted.

7. Consult FAQs and Support: Visit the Oxygen Advantage FAQs for troubleshooting tips and answers to common issues. They might have specific fixes for the problem you're encountering.

8. Contact Support: If none of the above steps work, contact the support team for further assistance. You can typically find the support contact information within the app or on the website.

Following these steps should help resolve the issue with the Oxygen Advantage app. If problems continue, checking for app-specific announcements regarding outages or problems can also be beneficial - learn more - learn more