App Containing System Extension to Be Activated Must Be in /Application folder

Scenario

You launch Firewall for Mac, and receive the message below:

Solution 1

Usually the issue occurs when the .app is not launched from Applications folder. Please try to move it there and retry.

Solution 2

If the Firewall.app already exists in Applications directory, proceed as follows:

1. Disable SIP (System Integrity Protection): https://developer.apple.com/documentation/security/disabling_and_enabling_system_integrity_protection
2. Restart your Mac
3. Login to macOS and run following command in Terminal utility:
   sudo xattr -dr com.apple.quarantine /Applications/Firewall.app