Device already exists in OpManager - why am I seeing this error ?

This error is occurs due to the following possible reasons:

• A device with same IP already exists in OpManager.
• A device with same name already exists in OpManager.
• Unique SysName might be enabled under Settings > Basic Settings > System Settings > Discovery > 'Unique System DisplayName' and the newly added device has the same Sysname of any of the existing device.