Custom configuration forms: translation access denied While creating custom configuration forms, I'm getting an access denied. But on the /translation page of the form only. Configuration form itself can be reached, filled and updated without problems.

Configuration does show up on the admin/config/regional/config-translation page but can't be translated for some reason. 

Any idea's? 

Overview of files:

schema.yml

faq.settings:
  type: mapping
  label: 'FAQ settings'
  mapping:
    faq_title:
      type: text
      label: 'Title'
    faq_text:
      type: text
      label: 'Text'
    faq_cta_label:
      type: text
      label: 'CTA label'
    faq_cta:
      type: text
      label: 'CTA'
...


routing.yml

aform.faq:
  path: '/admin/config/aform/faq'
  defaults:
    _form: '\Drupal\aform\Form\faqForm'
    _title: 'FAQ block'
  requirements:
    _permission: 'administer site configuration'
...


config_translation.yml

aform.faq:
  title: 'aform FAQ'
  base_route_name: aform.faq
  names:
    - faq.settings
...
For anyone stumbling towards a similar problem: it seems you have to set-up not only schema, routing and config_translations yml files but you also have to define each configuration in installation yml files so your config is picked up by Drupal.

So I had to include a faq.settings.yml file in /install of my custom module directory, like:

faq_title: ''
faq_text: ''
faq_cta_label: ''
faq_cta: ''
langcode: en


And boom you got yourself a translatable configuration form.