Why am I seeing the error "Error: Connection activation failed: No suitable device found for this connection (device nic0 not available because device is strictly unmanaged)."

Issue

• NetworkManager is not managing the physical Interfaces. While doing the configuration with nmcli, changes are not getting into effect.
• Seeing errors when trying to bring the device up with nmcli con up:

# nmcli con up nic0 
Error: Connection activation failed: No suitable device found for this connection (device nic0 not available because device is strictly unmanaged).

• Startup of NetworkManager not reporting the following in /var/log/messages nor system Journal:

manager: Networking is enabled by state file

• Startup of NetworkManager reports the following in /var/log/messages and system Journal:

manager: Networking is disabled by state file