Problem

TLS data session token error.

HRESULT error: FTPLIB_E_TLSDATASESSIONTOKENERROR (0x8004312B)

Cause

The FTP server is insecure, does not support Extended Master Secret Extension (EMS) and is not compatible with Microsoft's latest version of Schannel. The server usually runs an insecure and outdated TLS stack (e.g. OpenSSL older than version 1.1.0).

Solution

Contact the server administrator and request an update of the FTP server software and of OpenSSL.