FTP folder error(200,501) how to fix?

Question

IIS

Configured on the 2008R2 FTP server, registered rules in the firewall on ports. Everything opens inside the network, it does not want to from outside. You type the address, a login/password request window pops up, you enter it and an error appears:
An error occurred while opening a folder on the FTP server. Make sure you have permission to open this folder.
Details:
200 Type set to A
501 Server cannot accept argument.
There is no proxy, the Internet goes to the server through the TP-Link ER 5110 gateway. In it, through the virtual server, forwarding to the server is configured. What could it be and what is preventing the connection?

Answer 1

The issue is closed, ports for FTP were not forwarded on the gateway

Answer 2

tyts