INVALID_KEY_OR_REF on NetSuite: Invalid reference key error when creating/updating records via SuiteScript, CSV, or Integrations. — Root cause: This error occurs when an integration, SuiteScript, or CSV import attempts to set a List/Record field using a value that does not exist or is inactive in the target NetSuite environment. It most commonly happens with mismatched Internal IDs, using text instead of Internal IDs, or referencing records belonging to a different subsidiary. — If the ID exists, is active, and subsidiary alignment is correct, but the error persists, check for conflicting User Event scripts or Workflows that might be changing the value dynamically during the save process. Contact NetSuite Support if the issue isolates to a core standard field with no scripts attached.