"Error: connection activation failed: Device not managed by NetworkManager or unavailable" after moving machine

[Aaron Gray]

Hi,

"Error: connection activation failed: Device not managed by
NetworkManager or unavailable"

I am getting the above error and have tried all my normal mods to try
and get a connection.

I did move the SATA drive from one machine to another and back,
changing the MAC address and putting it back in the process.

I have tried adding 'NM_CONTROLLED="yes"' to
/etc/sysconfig/network-scripts/ifcfg-em1

but still am not able to get it to work.

As I cannot connect to the internet on this device I cannot do any yum
reinstalls.

Hope you can help,

Aaron