NGINX with Gunicorn: error 502 bad gateway - nginx

Question

I'm trying to run a web application with a SSL certificate on port 443.
To do so, I'm using Nginx as web server and Gunicorn as application server (running a Flask project).
I'm using a socket as proxy pass but I keep getting 502 bad gateway.
Here is my command with which I launch Gunicorn (works fine until I remove the port from the URL):
gunicorn --workers 4 --bind unix:webapp.sock -m 007 --certfile "/etc/ssl/certs/domain.chained.crt" --keyfile "/etc/ssl/certs/domain.key" 'wsgi:app'
And this is my nginx.conf:
# For more information on configuration, see:
# * Official English Documentation: http://nginx.org/en/docs/
# * Official Russian Documentation: http://nginx.org/ru/docs/
user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log;
pid /run/nginx.pid;
# Load dynamic modules. See /usr/share/doc/nginx/README.dynamic.
include /usr/share/nginx/modules/*.conf;
events {
worker_connections 1024;
}
http {
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
access_log /var/log/nginx/access.log;
sendfile on;
tcp_nopush on;
tcp_nodelay on;
types_hash_max_size 4096;
client_body_timeout 999;
client_header_timeout 999;
keepalive_timeout 999;
fastcgi_buffers 8 16k;
fastcgi_buffer_size 32k;
fastcgi_connect_timeout 999;
fastcgi_send_timeout 999;
fastcgi_read_timeout 999;
include /etc/nginx/mime.types;
default_type application/octet-stream;
# Load modular configuration files from the /etc/nginx/conf.d directory.
# See http://nginx.org/en/docs/ngx_core_module.html#include
# for more information.
include /etc/nginx/conf.d/*.conf;
server {
listen 80;
listen [::]:80;
server_name _;
root /usr/share/nginx/html;
# Load configuration files for the default server block.
include /etc/nginx/default.d/*.conf;
error_page 404 /404.html;
location = /404.html {
}
error_page 500 502 503 504 /50x.html;
location = /50x.html {
}
}
# Settings for a TLS enabled server.
#
# server {
# listen 443 ssl http2;
# listen [::]:443 ssl http2;
# server_name _;
# root /usr/share/nginx/html;
#
# ssl_certificate "/etc/pki/nginx/server.crt";
# ssl_certificate_key "/etc/pki/nginx/private/server.key";
# ssl_session_cache shared:SSL:1m;
# ssl_session_timeout 10m;
# ssl_ciphers HIGH:!aNULL:!MD5;
# ssl_prefer_server_ciphers on;
#
# # Load configuration files for the default server block.
# include /etc/nginx/default.d/*.conf;
#
# error_page 404 /404.html;
# location = /40x.html {
# }
#
# error_page 500 502 503 504 /50x.html;
# location = /50x.html {
# }
# }
include /etc/nginx/sites-enabled/*.conf;
server_names_hash_bucket_size 64;
}
And my web application conf in the sites-available folder:
server {
listen 443 ssl;
server_name domain www.domain;
ssl_certificate /etc/ssl/certs/domain.chained.crt;
ssl_certificate_key /etc/ssl/certs/domain.key;
location / {
proxy_set_header Host $http_host;
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://unix:/path/to/sock/webapp.sock;
}
}
This conf has been symbolically linked.
I have no idea why this is not working, as Nginx is not even logging anything!
I tried multiple things but I keep gateway the 502 error.
Does anyone have any idea? Thanks in advance