Copy between WD MyCloud device

I am trying to copy from my WD MyCloud drive to my MyCloud EX2 Ultra to my but every time I try using the FTP downloader, it says download fails. What am I doing wrong?

What is the specific FTP error? Are you trying to FTP to a remote My Cloud?

If possible its better to have both My Cloud devices on the same local network and use either Windows File Manager or Mac Finder to copy from one My Cloud to another. Or use SSH and issue a copy or rsync command to copy files from one My Cloud to another.

If trying to FTP to a remote My Cloud one has to enable port forwarding on the remote router that the remote My Cloud is connected to so that router passes the FTP port (21) to the remote My Cloud.