SFTP and FTPS access requires IP address whitelisting
SFTP \ FTPS connections require that customers register all public IP addresses that connect to the Thru services via these protocols.
To register an IP address the customer must provide the public IP address of the client connecting to the Thru service via one of the secure FTP connections.
If you don’t know the IP address, you can point a browser to https://whatismyipaddress.com/ and the IP address will be displayed.
Next, send an email to email@example.com to request the IP address(es) be whitelisted for FTP connectivity.
Note : this request should come via the customer (not directly from the customer's customer)