docker-compose.yml – yaml: could not find expected ':'

I am trying to create a docker-compose.yml file from 0 following this guide.

When I try to run the container I get the following error: yaml: line 29: could not find expected ':'

I’ve read everywhere and I find indentation problems, but I haven’t been able to tell why my file won’t run, any help would be Highly apreciated. My docker-compose.yml file contains the following:

version: "3.9"
########################### NETWORKS
# You may customize the network subnet (192.168.89.0/24) below as you please.
# Docker Compose version 3.5 or higher required to define networks this way.

networks:
  default:
    driver: bridge
  npm_proxy:
    name: npm_proxy
    driver: bridge
    ipam:
      config:
        - subnet: 192.168.89.0/24
########################### EXTENSION FIELDS
# Helps eliminate repetition of sections
# More Info on how to use this: https://github.com/htpcBeginner/docker-traefik/pull/228

# Common environment values
x-environment: &default-tz-puid-pgid
  TZ: $TZ
  PUID: $PUID
  PGID: $PGID

# Keys common to some of the core services that we always to automatically restart on failure
x-common-keys-core: &common-keys-core
  networks:
    - npm_proxy
  security_opt:
    - no-new-privileges:true
  restart: always

# Keys common to some of the dependent services/apps
x-common-keys-apps: &common-keys-apps
  networks:
    - npm_proxy
  security_opt:
    - no-new-privileges:true
  restart: unless-stopped

# Keys common to some of the services in media-services.txt
x-common-keys-media: &common-keys-media
  networks:
    - npm_proxy
  security_opt:
    - no-new-privileges:true
  restart: "no"

########################### SERVICES
services:
################ FRONTENDS
# Nginx Proxy Manager - Reverse Proxy with LetsEncrypt
  npm:
    <<: *common-keys-core # See EXTENSION FIELDS at the top
    container_name: nginx-proxy-manager
    image: 'jc21/nginx-proxy-manager:latest'
    # For Static IP
    networks:
    # For Static IP
      npm_proxy:
        ipv4_address: 192.168.89.254 # You can specify a static IP
    # For Dynamic IP
    # networks:
    #  - npm_proxy
    ports:
      - '80:80' # Public HTTP Port. Port Forwarding on Router is ON.
      - '443:443' # Public HTTPS Port. Port Forwarding on Router is ON.
      - '81:81' # Admin Web Port. Port Forwarding on Router is OFF. Internal Home Network Access only - 192.168.89.254:81.
    volumes:
      - $DOCKERDIR/appdata/npm/config:/config
      - $DOCKERDIR/appdata/npm/letsencrypt:/etc/letsencrypt
      - $DOCKERDIR/appdata/npm/data:/data
    environment:
      DB_SQLITE_FILE: "/config/database.sqlite"
      DISABLE_IPV6: 'true'

I’ve tried reviewing the indentation, and changing some environment variables definitions ex:
TZ: $TZ to - TZ=$TZ