Network Manager: device not managed

Wait, what's going on? Device not managed? But I didn't even do anything I swear! Here's how to fix it, solution found on ask Ubuntu.
Open up your NetworkManager config file and change the line managed=false to managed=true.

sudo vim /etc/NetworkManager/NetworkManager.conf

Then, restart the network-manager service.

sudo service network-manager restart 

Everything should work fine now.