Hi there! It sounds like you're experiencing a frustrating issue with the Fios TV Mobile app showing a black screen. I completely understand how annoying that can be. Let's troubleshoot this together.

To start, could you let me know if you've tried any steps already, like restarting the app or your iPhone? Here's a simple method we can go through:

1. Close and Relaunch the App: Sometimes, just closing the app completely and then reopening it can solve temporary glitches. To close the app, swipe up from the bottom of the screen (or double-click the home button if you have one) and swipe left or right to find the app, then swipe it up to close it. After that, reopen the Fios TV app.

2. Restart Your iPhone: A quick restart can often clear up many issues. Just hold the side button and either volume button until you see the slider, then slide to power off your device. After it’s off, turn it back on.

3. Check Your Internet Connection: Make sure your iPhone is connected to a stable Wi-Fi network. You can test your connection by browsing a website or streaming something else.

4. Update the App: Ensure the Fios TV app is up-to-date by checking the App Store for any available updates. Sometimes, updates contain fixes for existing issues.

5. Reinstall the App: If the above steps don’t work, you might want to delete the app and reinstall it. To do this, press and hold the app icon until you see the option to delete, then reinstall it from the App Store.

If you've tried all these steps and are still facing the black screen issue, we can look into some more advanced troubleshooting steps together, or I can check for any known app issues. Let me know how it goes!