I'm trying to import records from a CSV file to a "junction" object in Salesforce. This junction object has 2 parents. I'm trying to use the External ID Column drop-down list for each of the required foreign key fields. For the 1st parent, I can select a field from the Target in the "External ID Column" okay. However, when I try to select a a field from the Target in the "External ID Column" for the 2nd field, the dropdown list is blank and I cannot select anything.
Do you have any suggestions how I can make this work?