Can't upload via ProFTPd

Have installed proftpd and all I have done is change the default location so when you log in via ftp you are taken to a hard drive mounted at /mnt/USB_Caddy1

open my ftp software, connect, see folder on pi.
Try to uipload. get error.

Any ideas what I need to try/ do?


many thanks for your message. I tested ProFTP on my RPi3B+. As well I changed FTP root folder to an external USB stick without issues. Pls can you share the error message you are facing.