"It's failing" is not very useful problem description.
Anyway, the E:\ftp\in\test\files\ looks like a physical path on the remote server valid on the server only. Not FTP path exposed to the world. That will more be like /files/ or /test/files. Login with GUI and see yourself, what is the actual FTP path syntax of your server like.
See also https://winscp.net/eng/docs/faq_script_vs_gui#paths
If this does not help, post a session log file of a successful upload from WinSCP GUI.

I'm trying to upload csv files to a remote directory via script.

The home directory for the FTP site I'm connecting to is: E:\ftp\out\test\files
I only have permissions to write to E:\ftp\in\test\files\. Is my script below correct? It's failing and I can't figure out if it's my script or a permissions issue on the target folder.

Here is my script:

Thank you