@Ibmer: Thanks for sharing your knowledge.

You can set your FTP server up this way but if not an admin then just setting the home directory within the WinSCP connection properties for the IBM server will suffice. Specifically under Advanced site settings, then in under Directories properties set the Remote directory to a location you are trying to access within the IFS. Once you set your home directory within the IFS you should be able to traverse the files and directories within as long as you have the proper permission to the folders and files you are trying to access.

@css0013: See https://winscp.net/eng/docs/rawsettings#postlogincommands

Is there a way to pass on site namefmt 1 through command line rather than GUI?

@Guest: This is documented here:
Can I connect to a mainframe server? (e.g. VMS, MVS, AS/400)

Hello, a way to solve this temporarily is to execute the command SITE NAMEFMT 1 and that will shift the remote iSeries into the expected naming mode.

Thanks for sharing the instructions.

Just for info about "File must be specified by library/file.member"
and "I am using this on iSeries and it works on some of the systems but not all of them."

The FTP server on IBMi (successor of model AS/400, but everyone uses the old name) has lots of attributes.
One of them sets the FTP default target: from/into the DB2 database library system, or from/into the Unix file system on the machine.
The error message indicates that DB2 is set, but a Unix path is set in WinSCP.

Check and change this with command CHGFTPA + F4 to prompt the settings. Switch all parameters on using F9. Display the parameter names with F11. Page down to NAMEFMT and CURDIR.
Cursor position plus F1 explains always everything.
NAMEFMT = *PATH sends all incoming FTP connections at startup into IBMi's Unix server.
CURDIR = *HOMEDIR means: use user's home directory from his user profile. To check it, use DSPUSRPRF username, and page down to the very end. You'll see e.g. /home. Use CHGUSRPRF to change it.

If you log in from WinSCP now, you will be in /home, and the error message above will not show up.

Of course, like on any Unix based system, there is a fancy-mousy-clicky surface for all of this, as software or for browser. But command line is faster.

@Guest: Please attach a full log file both from a system where WinSCP works and where it does not? (using the latest version of WinSCP).

I am using this on iSeries and it works on some of the systems but not all of them.
I am checking to see if this has an update to correct.

I'm afraid WinSCP cannot deal with IBM AS/400 (nor with VMS).

This issue is being tracked already:
Issue 49 – Support for non-Unix-like systems with FTP

Let me also add that I get this error message as well when I use the ls command. It almost seems like some type of configuration issue, but I have uninstalled and reinstalled the software with no success. Also after reading further on the subject of VMS, I do not believe that the server is VMS.

Being that I pretty much have no idea what VMS is, I'm going to go out on a limb and say no.

I'm using Windows XP, and I am trying to send to an IBM AS/400 server. Does this answer the question?

Is it VMS?

When trying to send a file to my FTP server I get the following. I have no issues downloading a file from the server, only when I'm sending. Any suggestions would be greatly appreciated. Please let me know if there is more information you might need.