To resolve issues with the NFL app not opening, follow these detailed steps:

1. Check for Updates: Ensure both your NFL app and your device's operating system are up to date. This can often fix bugs that prevent the app from opening.

2. Force Close and Restart the App:
- Swipe up on your screen and find the NFL app in your recent apps.
- Swipe it away to close it completely.
- Reopen the app to see if it launches properly - learn more.

3. Log Out and Log Back In: Sometimes, logging out can refresh your connection to the service.
- Open the app (if possible).
- Navigate to account settings and log out.
- Wait a moment, then log back in.

4. Clear Cache and Data:
- Go to your device's Settings.
- Tap on Apps or Applications and find the NFL app.
- Select Storage, then choose Clear Cache and Clear Data.
- This step helps to reset the app's stored data - learn more.

5. Uninstall and Reinstall the App:
- Tap and hold the NFL app icon on your home screen.
- Select uninstall and confirm the action.
- Go to the Play Store, search for the NFL app, and install it again.

6. Check Internet Connection: Make sure your device is connected to a stable internet connection, as issues can arise from network problems. Switch between Wi-Fi and mobile data to rule out connectivity issues.

7. Restart Your Device: A simple restart can refresh your system and resolve any temporary glitches.

8. Verify Permissions: Ensure that the NFL app has the necessary permissions enabled:
- Go to Settings, then Apps, and select the NFL app.
- Check permissions and enable location services if needed.

9. Contact Support: If the app still fails to open, consider reaching out to NFL Support for assistance - learn more.

By following these steps, you should be able to troubleshoot and resolve issues with the NFL app not opening.