When using a Data Connector import rule, if any lookup key other than Resource Name is used, this will cause one of two issues:
There is no error message when "Create resources if doesn't exist" is checked. If this is unchecked, the import log error will be:
"Entire row x skipped. Importing this row wold create a new resource in the NS and resource creation has been disabled for this import rule."
There is a defect in Symantec Management Platform 7.5: Etrack 3361171. In other cases the dataclass field that is being used for the resource lookup key is not actually populated with data in existing resources.
If using Symantec Management Platform 7.5 upgrade to Symantec Management Platform 7.5 HF1 or higher to resolve this issue.
If using Serial Number as the Resource Lookup key for computers, the problem may be that the Serial Number dataclass used by the import rules has not been populated (Import Rules use the CMDB dataclass rather than the Inventory dataclasses for Serial Number). Run the Inventory to Asset Synchronization task under Manage>Jobs and Tasks>System Jobs and Tasks>Service and Asset Management>CMDB. This automatically populates the Serial Number dataclass with serial numbers collected by inventories.