When Working from home and/not using VPN connection do not establish

Hi, working in office I don't have issue to connect to a SFTP Vendor server but when working at home and using or not VPN connection do not establish.
My Technician request "What are the requirements to connect if working from home".
Regards

Is this even a WinSCP question? If it is, can you connect with any other SFTP/FTP client?