'''Issue Summary:''' When disconnecting from a corporate Cisco AnyConnect VPN on macOS, Firefox completely loses its internet connection and throws network errors. Other browsers (Chrome, Safari, Edge) continue working perfectly on the home network. Standard troubleshooting steps—like clearing Firefox's DNS cache, changing proxy settings to "No Proxy", turning off DNS over HTTPS (DoH), and flushing system DNS—do not resolve the issue. '''Root Cause:''' Cisco AnyConnect locks low-level socket configurations and routing rules within the active Firefox user profile (prefs.js). Even after the VPN is disconnected, Firefox remains bound to the dead corporate pipeline, a behavior that standard settings menus cannot override. '''Proven Solution:''' The only way to clear the corrupt VPN socket locks is to completely reset the internal profile architecture:Open Firefox, type about:support into the address bar, and press Enter.Look at the top right of the page and click the "Refresh Firefox..." button. Accept the prompt. Firefox will close, securely back up your bookmarks/passwords, generate a fresh profile, and restart.Internet access will instantly return to normal. (Note: You will just need to reinstall your extensions afterward).