An error occurred opening the folder on the ftp server

Clearapps network inventory
software.

An error occurred opening the folder on the ftp server
550 The system cannot find the file specified

Situation: the client install and add FTP on their Windows 2008 R2 by following this article: How to install and add FTP Site in Windows 2008 R2. They can access the FTP site internally but not in the Internet.

Troubleshooting: 1. The Firewall doesn't block the port 21 and we can telnet it from the Internet.
2. We can logon the FTP using FTP command.
3. The issue seems to be Passive mode problem. To fix it, Open IP and navigate to Tools>Options> Advanced.
4. Uncheck the “Use Passive FTP (for firewall and DSL modem…).
2.Check the “Enable FTP folder view (outside of Internet Explorer”.

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