Hello
Thank you for your question and reaching out. I can understand you are having issues related to connect to FTP .
Make sure the application pool has full control permission to virtual directory. Or an easier way is to remove the ftp site and application pool and create a new one.
Please try disable firewall and antivirus software temporarily to make sure your access would not be blocked.
According to the error message, I suspect the issue might be caused by your access right. Make sure you have the access privilege.
Opening Ports in the Firewall
https://learn.microsoft.com/en-us/previous-versions/sql/sql-server-2008/ms345310(v=sql.100)?redirectedfrom=MSDN
Enabling Protocols
https://learn.microsoft.com/en-us/previous-versions/sql/sql-server-2008/ms345306(v=sql.100)
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