I have successfully installed odoo (11.0 Community Edition) along with wkhtmltopdf on Ubuntu 18.04

The version of wkhtmltopdf is 0.12.5, I get deb package(wkhtmltox_0.12.5-1.bionic_amd64.deb) from download page(https://github.com/wkhtmltopdf/wkhtmltopdf/releases/tag/0.12.5).

The created PDF report is fine with Odoo serve web pages by itself.

However, the report lost its style when set a reverse proxy (Nginx) for this odoo.

The config files for Nginx and Odoo are list blow, are there anyone can give me advise for this issue?

user www-data;
worker_processes auto;
pid /run/nginx.pid;
include /etc/nginx/modules-enabled/*.conf;

events {
	worker_connections 768;
	# multi_accept on;
}

http {
        upstream backend-odoo11 {
            server 127.0.0.1:8011;
        }
        upstream backend-odoo11-im {
            server 127.0.0.1:8711;
        }

        server {
            listen 443 ssl;
            ssl_certificate     pem.crt;
            ssl_certificate_key pem.key;
            location / {
                root html;
                index index.html;
            }
        }

        server {
            listen 9011 ssl;
            ssl_certificate     pem.crt;
            ssl_certificate_key pem.key;

            location / {
                proxy_pass http://backend-odoo11;
                proxy_read_timeout 600;
                client_max_body_size 0;
            }

            location /longpolling {
                proxy_pass http://backend-odoo11-im;
                client_max_body_size 0;
            }

        }
}

[options]
; This is the password that allows database operations:
; admin_passwd = admin
db_host = False
db_port = False
db_user = odoo
db_password = False
;addons_path = /usr/lib/python3/dist-packages/odoo/addons
addons_path = /var/lib/odoo/liontech,/var/lib/odoo/liontech_themes,/var/lib/odoo/auto_backup
http_interface = 127.0.0.1
http_port = 8011
limit_time_real = 1200
logrotate = True
longpolling_port = 8711
proxy_mode = True
workers = 6