You can update sysobject id for any device by following the steps given below:
Go to Settings > NCM > Update SysOID
Select the device(s) you want to update SysOID for
Select appropriate SNMP profile(s) for the given devices
NCM will trigger the updation process, which takes some time to complete (depending upon the no. of devices selected).
You can check the updated SysObjectID under Settings > NCM > Device SysOID Mapping page.
You can also click on Update link mentioned in front of device name in 'Device SysOID Mapping' page to access the 'Update SysOID' page.