```ruby
module VoluntaryClassifiedAdvertisement
  class Engine < ::Rails::Engine
    config.i18n.load_path += Dir[File.expand_path("../../../config/locales/**/*.{rb,yml}", __FILE__)]
    
    config.to_prepare do
      Voluntary::Navigation::Base.add_product('classified-advertisement', t('workflow.user.products.classified_advertisement.title'))
    end
  end
end
```

Use I18n.t instead of t.
user
```ruby
module VoluntaryClassifiedAdvertisement
  class Engine < ::Rails::Engine
    config.i18n.load_path += Dir[File.expand_path("../../../config/locales/**/*.{rb,yml}", __FILE__)]
    
    config.to_prepare do
      Voluntary::Navigation::Base.add_product('classified-advertisement', I18n.t('workflow.user.products.classified_advertisement.title'))
    end
  end
end
```
assistant