Spreed WebRTC, websocket connection to wss://sub.domaine.com/ws failed

Hello, I followed a tutorial to install spreed-webrtc-snap on VPS linux 18.04 https://www.fosslinux.com/45051/how-to-install-spreed-webrtc-server-on-ubuntu.htm

This tutorial did not really treat the HTTPS part.

I have a subdomain, with a valid let’s encrypt certificate. Spreed WebRTC running on 8443 port, and coturn server on 8444 port.

Here is the vhost config file

<IfModule mod_ssl.c>
<VirtualHost *:443>
    ServerName sub.domain.com

        SSLEngine on
        SSLStrictSNIVHostCheck Off
        SSLProxyEngine On
        SSLProxyCheckPeerCN Off
        SSLProxyCheckPeerName Off
        SSLProxyVerify none

<Location />
      ProxyPass https://127.0.0.1:8443/
      ProxyPassReverse https://127.0.0.1:8443/
    </Location>

    <Location /ws>
       ProxyPass wss://127.0.0.1:8443/
    </Location>
    ProxyVia On
    ProxyPreserveHost On
    #RequestHeader set X-Forwarded-Proto 'https' env=HTTPS

SSLCertificateFile /etc/letsencrypt/live/sub.domain.com/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/sub.domain.com/privkey.pem
Include /etc/letsencrypt/options-ssl-apache.conf
</VirtualHost>
</IfModule>

After I made some modifications; here is the result:

1) Accessing by web address when I enter https://sub.domain.com, the UI loads (not completely), because of this error that displays in browser console.

 websocket connection to wss://sub.domaine.com/ws failed

2) Accessing by ip address When I enter IP as https://ip_address:8443, there is two cases; a) Kaspersky running Kaspersky prompts me if I want to continue to the dangerous website (this is normal cause there is no certificate for ip address), I click yes. Kaspersky generates its own certificate (I guess), then, the UI loads completely and the spreed webrtc works really great, I was able to make video call between 2 computers. b) Kaspersky not running This time, it’s the web browser that asks me if I want to continue to dangerous site, when I click yes, the UI do not load completely and I receive the same error on console when I access by web address

 websocket connection to wss://ip_address:8443/ws failed

The goal is that webrtc runs when accessing it by web address, I do not understand the problem.

Any help? Thanks.