The specified TRANSFORMFIELD element in the specified Lookup transformation is missing a REF_FIELD attribute in the XML file.
Edit the XML file and enter a REF_FIELD attribute. Make sure the REF_FIELD attribute matches the spelling of the TRANSFORMFIELD element it references. Or, export the object again and then import it.
The specified TRANSFORMFIELD element in the specified Lookup transformation contains a value for the REF_FIELD attribute that does not match another TRANSFORMFIELD element. Either the REF_FIELD attribute references a TRANSFORMFIELD that does not exist, or the spelling does not match the TRANSFORMFIELD name.
Edit the XML file and verify the REF_FIELD attribute matches the name of another TRANSFORMFIELD element. Or, export the object again and then import it.