Unable to login over FTP: 530 User cannot log in, home directory inaccessible

Symptoms

1. Plesk server is behind NAT.

2. Unable to connect to the server over FTP using IP address 203.0.113.2:

   CONFIG_TEXT: 530 User cannot log in, home directory inaccessible

3. Unable to open Subscriptions > example.com > File Sharing:

   CONFIG_TEXT: Filesharing: Internal error: Error in cURL request: Recv failure: Connection was reset
   Unable to load folders list.

4. IP address 203.0.113.2 is assigned to the domain example.com in Domains > example.com > Web Hosting Settings.

5. There are at several public IP addresses Plesk > Tools & Settings > IP Addresses, including 203.0.113.2.

6. IP address 203.0.113.2 does not exist on the server:

   C:\> ipconfig | findstr 203.0.113.2
   C:>

Cause

Incorrect network configuration.

Resolution

Review network configuration and make sure that the public IP address is assigned to an existent private IP address.

After that, assign domains to the existing IP addresses.