To address the issue of being unable to open the Meitu - Photo & Video Editor app after reinstalling it, follow these comprehensive steps:

1. Force Close the App:
- First, ensure that the app is not running in the background. You can do this by opening the activity monitor (found in Applications > Utilities), finding Meitu, and quitting the process.

2. Restart Your Device:
- Restarting your device can resolve many underlying issues. To do this, click on the Apple logo in the top left corner and select "Restart."

3. Check for Updates:
- Make sure your OS X version is up to date. Go to the Apple menu, select "System Preferences," and then "Software Update." If any updates are available, install them.

4. Clear App Cache:
- Although macOS does not have a dedicated cache clear option like mobile OS, you can navigate to Library/Caches by opening Finder, pressing Cmd + Shift + G, typing in ~/Library/Caches, and deleting any subfolders related to Meitu.

5. Reinstall the App:
- Uninstall the app completely by dragging it to the Trash. Afterwards, download the latest version of Meitu from the official website or the App Store and reinstall it.

6. Check Permissions:
- Ensure that Meitu has the necessary permissions to operate. Go to "System Preferences," then "Security & Privacy." Look under the "Privacy" tab and ensure Meitu is allowed to use the camera, microphone, and any other relevant permissions.

7. Contact Support:
- If the above steps do not work, contact Meitu's support for assistance. They may provide additional troubleshooting steps or acknowledge any ongoing app issues. You can report bugs directly on the Meitu support page - learn more.

8. Check for Common Issues:
- Sometimes, the app struggles with background processes or requires additional software dependencies. Look for common issues with similar apps or any updates about bugs on forums or community support pages.

9. Refer to Video Guides:
- If possible, watch helpful tutorial videos on platforms like YouTube that might offer visual assistance on fixing app opening issues, such as How To Fix Not Opening On Meitu App 2024 - learn more.

If after following these steps the app still does not open, consider checking community discussions or forums for similar issues.