Question Plesk Obsidian Ubuntu - Unable to connect with FTP

[IDSGmbH]

Hello,

first of all iam new to Plesk.
I have small problem with my Plesk FTP Configuration. I created the root user for my domain that can connect via SFTP Server, then i created a second user for my customer.
With that FTP-Account i am not able to connect. In my FileZilla i get the 20 second inactivity timeout error. I already checked some solutions.
The service is running.
lsof -i tcp:21 gives me this.

COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
xinetd 25793 root 5u IPv6 103439589 0t0 TCP *:ftp (LISTEN)

I tried to disable the Firewall, but iam not able to connect.

I am using Ubuntu 18.04 with Plesk Obsidian 18.0.26.

Thanks in advance