NGINX pagespeed CloudFlare ssl gives “NET::ERR_CERT_AUTHORITY_INVALID”

[SilverFoxA]

I have rebuilt nginx with pagespeed running on ubuntu. Here's my config file. When accessing the website via port 443 or ssl it gives me the following error NET::ERR_CERT_AUTHORITY_INVALID.

When I tried toggling pagespeed UseNativeFetcher off; I get the following error

nginx: [emerg] "pagespeed" directive "UseNativeFetcher" cannot be set at this scope. in /etc/nginx/sites-enabled/live:70

I'm not able to figure out where actually I'm doing wrong or what I'm missing out.

server {
  listen 80;
  listen [::]:80;
  server_name domain.com www.domain.com;

  # Redirect all traffic to SSL
  rewrite ^ https://$server_name$request_uri? permanent;
}

server {
    listen 443 ssl;
    listen [::]:443 ssl;

    # enables SSLv3/TLSv1, but not SSLv2 which is weak and should no longer be used.
    ssl_protocols SSLv3 TLSv1;

    # disables all weak ciphers
    ssl_ciphers ALL:!aNULL:!ADH:!eNULL:!LOW:!EXP:RC4+RSA:+HIGH:+MEDIUM;

    root /var/www/live/website/public;
    index index.php index.html index.htm;
    server_name domain.com www.domain.com;

    ## Access and error logs.
    access_log /var/log/nginx/access.log;
    error_log  /var/log/nginx/error.log info;

    ## Keep alive timeout set to a greater value for SSL/TLS.
    keepalive_timeout 75 75;

    ## See the keepalive_timeout directive in nginx.conf.
    ## Server certificate and key.
    ssl on;
    ssl_certificate /etc/ssl/site_ssl/public.pem;
    ssl_certificate_key /etc/ssl/site_ssl/private.key;
    ssl_session_timeout  5m;

    ## Strict Transport Security header for enhanced security. See
    ## http://www.chromium.org/sts. I've set it to 2 hours; set it to
    ## whichever age you want.
    add_header Strict-Transport-Security "max-age=7200";

    pagespeed on;
    pagespeed FileCachePath "/var/cache/ngx_pagespeed/";
    pagespeed RewriteLevel OptimizeForBandwidth;

    pagespeed EnableFilters trim_urls;
    pagespeed RewriteLevel OptimizeForBandwidth;
    pagespeed EnableFilters lazyload_images;
    pagespeed EnableFilters collapse_whitespace;
    #pagespeed UseNativeFetcher off;
    #pagespeed RespectXForwardedProto on;
    pagespeed FetchHttps enable,allow_self_signed,allow_unknown_certificate_authority;

    location ~ "\.pagespeed\.([a-z]\.)?[a-z]{2}\.[^.]{10}\.[^.]+" {
        add_header "" "";
        }

    location ~ "^/pagespeed_static/" { }
    location ~ "^/ngx_pagespeed_beacon$" { }

    pagespeed SslCertDirectory /etc/ssl/site_ssl;
    pagespeed SslCertFile /etc/ssl/site_ssl/public.pem;



    charset   utf-8;
    location / {
            try_files $uri $uri/ /index.php?$query_string;
        }
    location ~ \.php$ {
            try_files $uri /index.php =404;
            fastcgi_split_path_info ^(.+\.php)(/.+)$;
            fastcgi_pass unix:/run/php/php7.2-fpm.sock;
            fastcgi_index index.php;
            fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
            include fastcgi_params;
        }
    location ~* \.(?:jpg|jpeg|gif|png|ico|cur|gz|svg|svgz|mp4|ogg|ogv|webm|htc|svg|woff|woff2|ttf)$ {
          expires 1M;
          access_log off;
          add_header Cache-Control "public";
        }
    location ~* \.(?:css|js)$ {
          expires 7d;
          access_log off;
          add_header Cache-Control "public";
        }
    location ~ /\.ht {
            deny  all;
        }

}
TIA