So panel is installed, users are being added okay, FTP does login to users's directory. I am able to browse into public_html and see files. When I attempt to upload a file I get
550 Permission denied error.
I have checked that write_enable=YES in vsftpd.conf
Not sure why it's not allow the user to upload files to their own directory.
have you checked if you have enabled Locked Mod in user panel?
if locked mod is enabled you can not upload anything in public_html even as root user!