[Loadbalancing] error 404 but backend work fine

Hello all,

I try to load balance my web app using nginx but I get 404 instead my app.
All my backend (MS IIS) work fine when I try to query directely.

Can you help me please ?

Here is header when I query my IIS backend directely
See attached picture

Here is my nginx config:

upstream mywebapp {
ip_hash;
server 10.236.10.21:80;
server 10.236.10.22:80;
server 10.236.10.23:80;
server 10.236.10.24:80;
server 10.236.10.25:80;
server 10.236.10.26:80;
keepalive 16;
}
server {
listen 443 ssl;
server_name test.mywebapp.fr;
#client_max_body_size 10m;
ssl on;

location / {
proxy_pass http://mywebapp.fr;
proxy_http_version 1.1;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Host $host:443;
proxy_set_header X-Forwarded-Server $host;
proxy_set_header X-Forwarded-Port 443;
proxy_set_header X-Forwarded-Proto https;
proxy_set_header Connection "";
proxy_set_header Connection "";
proxy_read_timeout 60m;
proxy_pass_request_headers on;
}
}