Unable to Backup Device Configuration in NCM

Unable to Backup Device Configuration in NCM

Hi. I have added a new switch to the inventory, but when I try doing a backup of the switch's configuration I get the message 'Cannot trigger backup operation. Selection contains unmanaged device(s)..'

However, the device is managed so I don't understand why the error is showing up.
I've had a look for any clues but have had no luck so far. Thanks in advance for any help.