Deleting an Offering that was previously marked complete

Summary

I am trying to delete a duplicate record. I am unable to reset the activity through the manage activities screen and when when I try to edit it though a spreadsheet it saying the file is locked.

Content

Two employees were accidentally added to the same offering twice and marked complete through a mass action. I am unable to reset their activities in UI and am trying to do it though an HDL load.

The HDL load with the Business Object "Learning Record Activity Attempt" I received an error saying "ActivityAttempt record creation or updation is not allowed". I am now trying to change the status on the Offering through an HDL load on the "Learning Record" Business Object but each load I have have attempted errors saying I need to add another value to the spreadsheet. The most recent error said that I need to add Assignment Attribution Code but I am not sure where to find that value.