Sidekiq 5 is not working with AWS ELB and rails 5 api

Question

Ruby version: 2.3.1

Sidekiq / Pro / Enterprise version(s): 5.0

Rails: 5.0.2

I've followed this tutorial so I could use sidekiq to send emails in my rails api app. The app is published on AWS ElasticBeanstalk with Puma.

When an user registers, they should receive an email (through devise). No error is shown, no log at sidekiq.log is generated. I don't know what is going on, the emails simply aren't delivered.

initializers/devise_async.rb

Devise::Async.setup do |config|
  config.enabled = true
  config.backend = :sidekiq
  config.queue   = :default
end

initializers/sidekiq.rb

rails_root = Rails.root || File.dirname(__FILE__) + '/../..'
rails_env = Rails.env || 'development'
redis_config = YAML.load_file(rails_root.to_s + '/config/redis.yml')
redis_config.merge! redis_config.fetch(Rails.env, {})
redis_config.symbolize_keys!
Sidekiq.configure_server do |config|
  config.redis = { url: "redis://#{redis_config[:host]}:#{redis_config[:port]}/12" }
end
Sidekiq.configure_client do |config|
  config.redis = { url: "redis://#{redis_config[:host]}:#{redis_config[:port]}/12" }
end

config/redis.yml

development:
 host: 'localhost'
 port: '6379'
test:
 host: 'localhost'
 port: '6379'
production:
 host: 'xxxxx-xxxx-xxx.xxxxxx.xx.0001.sae1.cache.amazonaws.com'
 port: '6379'

config/sidekiq.yml

:concurrency: 5
:queues:
  - default

Last sidekiq log lines:

2017-05-06T02:16:10.579Z 8388 TID-grwqwpuzw INFO: Received USR1, no longer accepting new work
2017-05-06T02:16:10.584Z 8399 TID-gp30plzqo INFO: Received USR1, no longer accepting new work

Last nginx log lines:

172.31.14.103 - - [06/May/2017:02:20:51 +0000] "POST /v1/auth/ HTTP/1.1" 200 271 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.96 Safari/537.36"

2017/05/06 02:16:22 [warn] 15902#0: conflicting server name "localhost" on 0.0.0.0:80, ignored
2017/05/06 02:16:22 [warn] 15909#0: conflicting server name "localhost" on 0.0.0.0:80, ignored
2017/05/06 02:16:22 [warn] 15950#0: conflicting server name "localhost" on 0.0.0.0:80, ignored
2017/05/06 02:16:22 [warn] 15957#0: conflicting server name "localhost" on 0.0.0.0:80, ignored

Last puma log lines:

[11765] - Gracefully shutting down workers...
[11765] === puma shutdown: 2017-05-06 02:16:23 +0000 ===
[11765] - Goodbye!
=== puma startup: 2017-05-06 02:16:26 +0000 ===
=== puma startup: 2017-05-06 02:16:26 +0000 ===
/var/app/current/app/serializers/notification_serializer.rb:20: warning: redefining `object_id' may cause serious problems
[16011] - Worker 0 (pid: 16014) booted, phase: 0

It works fine on local machine.

Do you have some ideas?