Error: Form security failed

Hi all, I know this issue has been encounter by others before me but there doesn’t seem to be a concrete solution. Hopefully someone has a similar use set up as mine?

After setting up nginx to reverse proxy piwik over https only, I am getting the following login form error despite entering the correct credentials:
48 PM

Here is my nginx configuration:

server {
    listen         80;
    listen         [::]:80;
    server_name    127.0.0.1;
    return         301 https://$server_name$request_uri;
}

upstream app_servers {
    server piwik;
}

server {
    listen              443 ssl;
    server_name         localhost;
    ssl_certificate     /run/secrets/ssl_cert;
    ssl_certificate_key /run/secrets/priv_key;

    location / {
        proxy_pass http://app_servers;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        proxy_set_header Host localhost;
        proxy_cache_bypass $http_upgrade;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Host localhost;
        proxy_buffering off;
        proxy_set_header X-Real-IP $remote_addr;
    }
}

Piwik configuration:

[General]
assume_secure_protocol = 1
force_ssl = 1
proxy_host_headers[] = HTTP_X_FORWARDED_HOST
proxy_client_headers[] = HTTP_CLIENT_IP
proxy_client_headers[] = HTTP_X_FORWARDED_FOR
enable_trusted_host_check = 0

Docker-compose configuration:

version: "3.3"

services:
  db:
    image: mariadb:latest
    volumes:
      - /mnt:/var/lib/mysql
    deploy:
      replicas: 1
      restart_policy:
        condition: on-failure
    environment:
      MYSQL_ROOT_PASSWORD_FILE: /run/secrets/db_root_password
      MYSQL_DATABASE: piwik
    secrets:
      - db_root_password

  piwik:
    depends_on:
      - db
    image: piwik:latest
    volumes:
      - ./piwik/config.ini.php:/var/www/html/config/config.ini.php
    deploy:
      replicas: 3
      restart_policy:
        condition: on-failure
    ports:
      - 3000:80

  nginx:
    depends_on:
      - piwik
    image: nginx:latest
    volumes:
      - ./nginx/site.conf:/etc/nginx/conf.d/site.conf
    deploy:
      replicas: 3
      restart_policy:
        condition: any
        max_attempts: 100
    secrets:
      - priv_key
      - ssl_cert
    ports:
      - 443:443

secrets:
  priv_key:
    file: /etc/ssl/ssl.key
  ssl_cert:
    file: /etc/ssl/ssl.crt
  db_root_password:
    file: ./secrets/db_root_password.txt