Symptoms

• FTP user presents in /etc/passwd and in sys_users table of psa database
  

   MariaDB [psa]> select login from sys_users where id=11 \G 
   *************************** 1. row *************************** 
   login: examplelogin
   1 row in set (0.00 sec)

• In Plesk interface there is no FTP user with such a name.

Cause

Appropriate record is missing in ftp_users table of psa database.

Resolution

Add record in ftp_users table with corresponding values:

MariaDB [psa]> select id from domains where name = "example.domain";
+----+
| id |
+----+
| 1 |
+----+
1 row in set (0.00 sec)
MariaDB [psa]> select id from sys_users where login="examplelogin";
+----+
| id |
+----+
| 11 |
+----+
1 row in set (0.00 sec)

MariaDB [psa]> INSERT INTO ftp_users (dom_id,sys_user_id,permission) VALUES (1,11,0);
Query OK, 1 row affected (0.00 sec)

Please note the second value in this command, dom_id (domain id). It refers to main domain name of the subscription, and not to domain name of web site.