Expected <block end> , but found '?'

what does this error mean?

2019-04-10 14:53:31 ERROR (Thread-2) [homeassistant.util.yaml] while parsing a block collection
  in "/home/homeassistant/.homeassistant/configuration.yaml", line 67, column 3
expected <block end>, but found '?'
  in "/home/homeassistant/.homeassistant/configuration.yaml", line 75, column 3
2019-04-10 14:53:31 ERROR (MainThread) [homeassistant.bootstrap] Error loading /home/homeassistant/.homeassistant/configuration.yaml: while parsing a block collection
  in "/home/homeassistant/.homeassistant/configuration.yaml", line 67, column 3
expected <block end>, but found '?'
  in "/home/homeassistant/.homeassistant/configuration.yaml", line 75, column 3

my configuration.yaml

homeassistant:

  # Name of the location where Home Assistant is running
  name: Home

  # Location required to calculate the time the sun rises and sets
  latitude: 50.85
  longitude: 3.3

  # Impacts weather/sunrise data (altitude above sea level in meters)
  elevation: 0

  # metric for Metric, imperial for Imperial
  unit_system: metric

  # Pick yours from here: http://en.wikipedia.org/wiki/List_of_tz_database_time_zones
  time_zone: Europe/Brussels

  # Customization file
  # authentication providers
  auth_providers:
    - type: homeassistant
    - type: trusted_networks
      trusted_networks:
        - 192.168.0.0/24
    - type: legacy_api_password
      api_password: !secret api_password

# Configure a default setup of Home Assistant (frontend, api, etc)
default_config:

# Show the introduction message on startup.
# introduction:

# Uncomment this if you are using SSL/TLS, running in Docker container, etc.
http:
  ssl_certificate: /home/homeassistant/dehydrated/certs/xxxxxxxx.duckdns.org/fullchain.pem
  ssl_key: /home/homeassistant/dehydrated/certs/tientjesstraat.duckdns.org/privkey.pem
  base_url: tientjesstraat.duckdns.org:8123

# Discover some devices automatically
discovery:

# Sensors
sensor:
  # Weather prediction
  - platform: yr

# Text to speech
tts:
  - platform: google

group: !include groups.yaml
automation: !include automations.yaml
script: !include scripts.yaml

# mqtt Mosquitto
mqtt:
  broker: localhost
  username: mqttUser
  password: !secret mqtt_password
# switches
switch:
  - platform: mqtt
    name: "Verlichting living"
    icon: mdi:lightbulb-on
    command_topic: "cmnd/HA/living/power"
    state_topic: "stat/HA/living/POWER"
    qos: 1
    payload_on: "ON"
    payload_off: "OFF"
  retain: true
    state_on: "ON"
    state_off: "OFF"
#    optimistic: false
#    qos: 0
#    retain: false

# cloud:
google_assistant:
  project_id: HomeAssistant
  # api_key: !secret api_key
  exposed_domains:
    - switch
    - light
  entity_config:
    switch.kitchen:
      name: CUSTOM_NAME_FOR_GOOGLE_ASSISTANT
      aliases:
        - BRIGHT_LIGHTS
        - ENTRY_LIGHTS
    light.living_room:
      expose: false
      room: LIVING_ROOM
    group.all_automations:
      expose: false

It would help if you would share what line 67 and 75 are SPECIFICALLY.

My guess is that you have an extra space at the end of your lines.

EDIT: Actually, look at your “RETAIN” line

yeah, sorry, I was about to edit my post : the error is inside the switches block, but I think it is because the "retain: true " line is not correctly intended.

… and don’t use retain: true for lights.

It means the payload, published to command_topic, will be retained by the MQTT broker. This can have the undesirable effect of the light automatically turning itself on when either the broker or the light restarts (unless, of course, that’s the behavior you want).