Chat with Support and reference this article. Typically, these failures are caused by one of a few things. 

  1. Invalid records on a large file. For example, the address for a record may have a character in it causing the address to be split, which would cause the file to fail.  The database won't allow the records to be exported as they are.  Please ensure all records have valid addresses, free from extraneous spaces or characters.  It may help to open the record in TA, delete the address completely and re-enter it in your database.
  2. Partial imports were records actually went in but a certain number were ignored because they either have been mark as deleted in Sphere, the account id or name id combination on the file does not match what is in Sphere, or the record in Sphere is more recent or has no differences.
  3. FTP server maintenance can cause failures as well.