Fix 'NetworkManager is not running' Error on Linux

The error message 'NetworkManager is not running' indicates that the NetworkManager service, which manages network connections and settings on Linux-based systems, is not active. To fix this, follow these steps:

1. Open a terminal window.
2. Check NetworkManager status:

systemctl status NetworkManager

If it's not running, you'll see an error message or 'inactive' status.
3. **Start NetworkManager:**

sudo systemctl start NetworkManager

4. **Verify the service is running:**

systemctl status NetworkManager

If the service still doesn't start or you encounter issues, try reinstalling NetworkManager:

sudo apt-get install --reinstall network-manager

After reinstalling, repeat steps 2-4 to start NetworkManager.

**Note:** Commands may vary based on your Linux distribution. The instructions are for systems using systemd (e.g., Ubuntu, Fedora, CentOS).