Resends a failed fax as an entirely new fax, reusing the original document, recipient, subject, coversheet, language and image quality. The original entry is left untouched and nothing records that a retry happened, so calling this twice sends the fax twice — guard against duplicates yourself. Only a fax whose status is failed, whose failure reason is one that can be retried, and whose document is still available can be resent; anything else is a 422.