I can't get my menu to show even though I edited .menu_links.yml and .routing.yml properly.

Hi,

I have been porting my contrib to Drupal 8 for a while, and with the latest change about hook_menu_links_default being removed and menu_links.yml being added, I am stuck. Even though I have been examining core modules' code. Long story short, my link doesn't show up on /admin/config/system. Can you help me? Below are my files.

tcmb.menu_links.yml:

tcmb.tcmb_settings:
  title: Tcmb General Settings
  description: 'Configure Tcmb module.'
  route_name: tcmb.tcmb_settings
  parent: system.admin_config_system
  weight: 1
tcmb.tcmb_settings_currency:
  title: 'Tcmb General Settings'
  description: 'Configure Tcmb module.'
  route_name: tcmb.tcmb_settings
  parent: system_admin_config_system
  weight: 1
tcmb.gold_settings
  title: 'Gold settings'
  description: 'Configure Tcmb gold settings.'
  route_name: tcmb.gold_settings
  parent: tcmb.admin_config_system_tcmb_settings
  weight: 2
tcmb.other_settings:
  title: 'Other settings'
  description: 'Configure other settings.'
  route_name: tcmb.other_settings
  parent: tcmb.admin_config_system_tcmb_settings
  weight: 3
tcmb.other_settings_currency:
  title: 'Currency Settings'
  description: 'Configure other settings.'
  route_name: tcmb.other_settings_currency 
  parent: tcmb.tcmb_other_settings
  weight: 1
tcmb.other_settings_gold:
  title: Gold Settings
  description: 'Gold Settings'
  route_name: tcmb.other_settings_gold
  parent: tcmb.tcmb_other_settings
  weight: 2

tcmb.routing.yml:

tcmb.tcmb_settings:
  path: '/admin/config/system/tcmb-settings'
  defaults:
    _form: 'Drupal\tcmb\TcmbCurrencySettingsForm'
    _title: 'Tcmb General Settings'
  requirements:
    _permission: 'administer Tcmb'
tcmb.gold_settings:
  path: '/admin/config/system/tcmb-settings/gold-settings'
  defaults:
    _form: 'Drupal\tcmb\TcmbGoldSettingsForm'
  requirements:
    _permission: 'administer Tcmb'
tcmb.other_settings:
  path: '/admin/config/system/tcmb-settings/other-settings'
  defaults:
    _form: 'Drupal\tcmb\TcmbOtherSettingsForm'
  requirements:
    _permission: 'administer Tcmb'
tcmb.other_settings_currency:
  path: '/admin/config/system/tcmb-settings/other-settings/currency'
  defaults:
    _form: 'Drupal\tcmb\TcmbOtherSettingsForm'
  requirements:
    _permission: 'administer Tcmb'
tcmb.other_settings_gold:
  path: '/admin/config/system/tcmb-settings/other-settings/gold'
  defaults:
    _form: 'Drupal\tcmb\TcmbOtherGoldSettingsForm'
  requirements:
    _permission: 'administer Tcmb'

Regards,
K.