Privacy Settings: Go to Settings > Privacy > Camera. Ensure that 'Allow apps to access your camera' is turned on. This setting can also affect screen sharing.

Antivirus/Firewall: Check if your antivirus or firewall settings are blocking the screen sharing feature.

Security & Privacy: Navigate to System Preferences > Security & Privacy > Screen Recording. Make sure your browser is checked to allow screen sharing.

Accessibility Settings: Some apps may require access under 'Accessibility' in the Security & Privacy settings.

Distribution-Specific Settings: Linux distributions may have unique settings. Check your distribution's documentation for screen sharing permissions.