Hi there! I understand your Honkai Impact 3rd app on your phone won't boot up even after reinstalling, which must be quite puzzling. To help further, could you please tell me the following details?

1. What kind of phone are you using (brand/model and OS version)?
2. When you say it won't boot, does the app crash immediately, freeze on a loading screen, or just not open at all?
3. Have you noticed if this started happening after a specific update or event?
4. Are you connected to a stable network (Wi-Fi or mobile data)?

Once I know these, I can guide you through some steps. Meanwhile, here are a few things you can try:

1. Clear the app cache and data: Go to your phone’s Settings > Apps > Honkai Impact 3rd > Storage > Clear Cache, and Clear Data (Note: Clearing data may remove local settings but not your game account).

2. Check for any system or app updates: Make sure your phone's OS and the app itself are fully updated from the official store.

3. Restart your phone: Sometimes a simple reboot helps the system refresh resources.

4. Ensure you have enough free storage: Insufficient storage can prevent the app from launching.

5. Check that the app has all necessary permissions enabled, like storage and network access.

If none of those help, sometimes leftover files can cause issues even after reinstalling. In that case, uninstall the app, then use a file manager to ensure the Honkai Impact 3rd folder is completely removed from your device storage before reinstalling.

Please try these and let me know what happens. If the problem persists, I can walk you through more advanced troubleshooting or check for any known issues affecting your specific device or region.

Are you using Android or iOS phone? This info will help me customize the guidance better.