I ran into some similar issues while upgrading some of my sites. My problems were mainly because I wasn't using standard resourceful routes. The simplest way to fix this is to just specify each route manually. If you have a lot of similar patterns with other resources you could just write a function to create each route pattern.
routes.rb
delete 'subscriptions', to: 'subscriptions', as: :subscriptions
get 'subscriptions/edit', to: 'subscriptions#edit', as: :edit_subscriptions
Rails 4 Routes :
subscriptions DELETE /subscriptions(.:format) subscriptions#subscriptions
edit_subscriptions GET /subscriptions/edit(.:format) subscriptions#edit