Hi there! It sounds like you're having trouble opening the FreeStyle Libre 2 app because it's prompting you to allow access to critical alerts. Let's work through this together.

First, since you're using a Macintosh with OS X, it’s important to check a few settings to ensure everything is correctly configured for the app:

1. Check System Preferences:
- Open System Preferences on your Mac.
- Click on Notifications.
- In the list, find the FreeStyle Libre 2 app and make sure that "Allow Notifications" is enabled. You should also check that "Show notifications on Lock Screen" and "Show in Notification Center" are selected.

2. Check App Permissions:
- Go to System Preferences > Security & Privacy.
- Click on the Privacy tab and look for Notifications and Location Services.
- Make sure FreeStyle Libre 2 has permission to send notifications and access location if asked.

3. Reinstall the App:
- Sometimes, reinstalling the app can help refresh its permissions and settings. Simply uninstall the FreeStyle Libre 2 app, then download it again from the App Store.

4. Software Updates:
- Ensure your Mac is running the latest version of OS X available for your device. You can check this by going to System Preferences > Software Update.

If you’ve checked these settings and are still encountering issues, it may be worth addressing if there are any system updates needed or exploring whether any potential conflicts with other applications could be impacting the FreeStyle Libre app.

Please let me know what steps you've already tried, and we can dive into further troubleshooting if necessary!