Error: Invalid_key_or_ref: Import failed for SF record id <the id is specified>

Note: The name “SmartConnector” will be changing to the “Integration App” to more clearly establish that our pre-built Integration Apps are built on our flagship Integration Platform as a Service, integrator.io.  

Error:

Invalid_key_or_ref: Import failed for SF record id <the id is specified>.  
Reason: Invalid price reference key -1 for item.

Meaning:

This means that the product(s) on the Opportunity has not been synced to a NetSuite item.

Resolution:

Find the NetSuite id.  Edit the Salesforce Product to include the NetSuite item id.  Edit the NetSuite item to include the 18-character Salesforce id.