Sometime while creating Additional FTP account or Updating Domain user it shows following Error

Error: Unable to update FTP account: Unable to create web user: Update FTP user failed:
ftpmng --add-user failed: Empty error message from utility.

This problem comes when .Security file of the domain get corrupted. This file can be found at C:\Inetpub\vhosts\ OR D:\Inetpub\vhosts\ OR in the domain home directory. Rename the file to OLD.Security and run following command:

C:\Parallels\Plesk\admin\bin>websrvmng.exe --reconfigure-vhost
C:\> "%plesk_bin%\ftpmng.exe" --reconfigure-vhost

Above command will create a new .Security file based on the Plesk Database and then try to create new FTP user or try to update domain user.