MySqlException: Cannot add or update a child row: a foreign_key constraint fails

I have this error: "MySqlException: Cannot add or update a child row: a foreign_key constraint fails" on my C# project, when executing this code:

INSERT INTO networks (owner_name, name, password, ip, visible)
VALUES ('alex', 'alex_net', '1234', '192.168.1.1', 1)
ON DUPLICATE KEY
UPDATE name='alex_net', password = '1234', ip = '192.168.1.1', visible = 1;

But when I execute it on PhPMyAdmin it works perfectly.

Why does it fail on the aplication but works on PhPMyAdmin?

EDIT:
I’m using MySqlConnector/Mono

C# function that executes query:

public static bool InsertOrUpdateNetwork(MySqlConnection connection, NetworkSO networkData)
{
    string sql =
        $"INSERT INTO networks (owner_name, name, password, ip, visible) " +
        $"VALUES ('{networkData.ownerName}', '{networkData.name}', '{networkData.password}', '{networkData.ip}', {networkData.visible}) " +
        $"ON DUPLICATE KEY " +
        $"UPDATE name='{networkData.name}', password='{networkData.password}', ip='{networkData.ip}', visible={networkData.visible}";

    MySqlCommand cmd = new MySqlCommand(sql, connection);
    int result = cmd.ExecuteNonQuery();

    return result > 0;
}

SHOW CREATE networks & users:

CREATE TABLE networks (
 owner_name varchar(16) NOT NULL,
 name varchar(16) DEFAULT NULL,
 password varchar(16) DEFAULT NULL,
 ip varchar(15) NOT NULL,
 visible tinyint(4) NOT NULL,
 PRIMARY KEY (owner_name),
 UNIQUE KEY owner_name_UNIQUE (owner_name),
 CONSTRAINT fk_network_owner_name FOREIGN KEY (owner_name) REFERENCES users (name) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1

CREATE TABLE users (
name varchar(16) NOT NULL, 
password varchar(16) DEFAULT NULL, 
logged tinyint(4) DEFAULT NULL, 
PRIMARY KEY (name), 
UNIQUE KEY name_UNIQUE (name) 
) ENGINE=InnoDB DEFAULT CHARSET=latin1

Complete console log:

MySqlException: Cannot add or update a child row: a foreign key constraint fails (sql7721749.networks, CONSTRAINT fk_network_owner_name` FOREIGN KEY (owner_name) REFERENCES users (name) ON DELETE CASCADE ON UPDATE CASCADE)