Required fields missing error while inserting custom object record Salesforce

[BlueOcean_ProvePharm]

I am trying to insert a custom object record and that custom object record has a master detail relationship field and for that field I have provided 18 digit Id from the Salesforce , but when I am trying to load the data I am getting required fields missing error. What should be the input for look up or

master detail relationship fields in the mapping file.

[Anonymous]

I am afraid this sounds like a Salesforce issue. I believe that Salesforce would need a bit more information to answer this as well.