Installing Wordpress plugins

I am trying to launch a wordpress blog with docker compose. I have a working wordpress installation except I can’t install plugins. Here is my docker-compose.yaml file

version: '3'
services:
db:
container_name: ${DB_CONTAINER}
image: mysql:5.7
volumes:
- db_data:/var/lib/mysql
restart: always
environment:
 MYSQL_ROOT_PASSWORD: "${ROOT_PASSWORD}"
 MYSQL_DATABASE: ${WP_DB}
 MYSQL_USER: ${WP_USER}
 MYSQL_PASSWORD: ${WP_PASSWORD}

wordpress:
container_name: ${WP_CONTAINER}
depends_on:
- db
image: wordpress:latest
restart: always
expose:
- '80'
volumes:
- ${WP_CORE}:/var/www/html
- /home/chad/web/wordpress/wp-content:/var/www/html/wp-content
- /home/chad/web/wordpress/uploads.ini:/usr/local/etc/php/conf.d/uploads.ini
environment:
 WORDPRESS_DB_HOST: db:3306
 WORDPRESS_DB_USER: ${WP_USER}
 WORDPRESS_DB_NAME: ${WP_DB}
 WORDPRESS_DB_PASSWORD: ${WP_PASSWORD}
 LETSENCRYPT_HOST: ${DOMAIN_NAME}
 LETSENCRYPT_EMAIL: ${LETSENCRYPT_EMAIL}
 VIRTUAL_HOST: ${DOMAIN_NAME}
volumes:
 db_data:
networks:
default:
external:
 name: ${NETWORK}

I followed this guide https://www.tumatiki.com/2018/02/17/how-to-deploy-wordpress-with-docker-compose-and-lets-encrypt/

What is the error?
Need more information in order to help.