Embark on a journey through the digital realm with Network Manager, a stalwart companion for Linux users seeking connection to the vast online expanse. Though usually smooth sailing, occasional storms brew, such as the vexing 'Device not managed' error. Fear not, for a simple remedy awaits...
Steps to Triumph

First, Unveil the Terminal: Invoke the terminal by pressing Ctrl+Alt+T. Then, cast the spell: gksu gedit /etc/NetworkManager/NetworkManager.conf. Prepare to wield administrative prowess as the password beckons...

Next, Forge the Path: Venture into the depths of the NetworkManager.conf file. There, amidst the code, swap
managed=false
for managed=true
. Seal your edits and bid farewell to the editor, victorious.
Reboot Your PC or Network Manager: Opt for a system restart or, for a swifter solution, wield the terminal with the command: sudo restart network-manager.
Handy Pointers
- If the terminal trick falls short, endeavor to summon sudo apt-get install gedit into the terminal to conjure gedit, a nimble text editing sorcerer.