Inventory or order file from fulfillment center is not imported using Fulfillment Center functionality. Synchronization produces error
The import file contains invalid data. In this specific case it has multiple columns with the same name or empty column names.
1) Download the file from FTP to ensure it doesn't have empty columns
2) Open the file in excel and check for duplicated column names
3) If no duplicated columns can be seen, open the file in notepad and check there are no empty columns.
Fix the error in the file, or get your fulfillment center to correct the inventory feed file and retry the synchronization.