Wiki¶

If WordPress is unable to determine when requests are made over HTTPS, causing it to be incapable of serving HTTPS-specific content.
Web browsers nowadays usually prohibit loading insecure content within pages that are accessed via HTTPS, which results in predictable issues.

See SSL Insecure Content Fixer

The the fix is in wp-config.php add the following,

if (isset($_SERVER['HTTP_X_FORWARDED_PROTO']) && $_SERVER['HTTP_X_FORWARDED_PROTO'] === 'https') {
  $_SERVER['HTTPS'] = 'on';
} 

And in the NGINX config Add,

server {
    listen 443;
    server_name blog.ldev.app;
    ssl on;     ssl_certificate /etc/pve/local/nginx/ldev-ssl.pem;
    ssl_certificate_key /etc/pve/local/nginx/ldev-ssl.key;
    proxy_redirect off;
    location / {
        proxy_set_header        Host $host:$server_port;
        proxy_set_header        X-Real-IP $remote_addr;
        proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header        X-Forwarded-Proto $scheme;
        proxy_pass http://*YOUR IP AND PORT*;
    }
}

If your using Nginx Proxy Manager point to the root dir in Custom locations, and in the Advanced tab, use the Custom Nginx Configuration below

proxy_set_header        Host $host:$server_port;
proxy_set_header        X-Real-IP $remote_addr;
proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header        X-Forwarded-Proto $scheme;