Airflow + Nginx set up gives Airflow 404 = lots of circles

Question

I'm trying to set up Airflow behind nginx, using the instructions given here.

airflow.cfg file

base_url = https://myorg.com/airflow
web_server_port = 8081
.
.
.
enable_proxy_fix = True

nginx configuration

server {
    listen 443 ssl http2 default_server;
    server_name myorg.com;
    .
    .
    .

    location /airflow {
        proxy_pass http://localhost:8081;
        proxy_set_header Host $host;
        proxy_redirect off;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_set_header X-Forwarded-Proto "https";
    }
}

Airflow webserver and scheduler are up and running as systemd. When I try to access https://myorg.com/airflow/, it gives Airflow 404 = lots of circles.

What could be wrong? Really appreciate your help in getting this running.