The locale selection was disabled during migration to rails 5.1

Back again...

app/controllers/application_controller.rb

@@ -1,6 +1,6 @@
 # The top level controller, where can be centralised almost everything
 class ApplicationController < ActionController::Base
-  before_action :set_paper_trail_whodunnit, :discard
+  before_action :set_paper_trail_whodunnit, :set_locale, :discard
   # Prevent CSRF attacks by raising an exception.
   # For APIs, you may want to use :null_session instead.
   protect_from_forgery prepend: true, with: :exception