Sidekiq is not processing jobs

I was upgrading Sidekiq to v6 and Redis to v4 (Redis is running on AWS Elasticache). The Rails app is running on AWS EC2 instance. Since the upgrade, background jobs are not processing.

I thought that Redis might not be running - so I logged in to the EC2 instance and run ps aux | grep redis-server:

deployer   932  0.0  0.0  10472   940 pts/0    S+   18:10   0:00 grep --color=auto redis-server

And in the AWS dashboard, there's info that Redis is running.

I checked Sidekiq - ps aux | grep sidekiq:

deployer   982  0.0  0.0  10472   936 pts/0    S+   18:12   0:00 grep --color=auto sidekiq

Also, the URL /sidekiq is running and I can see there a growing Enqueued section with the jobs that are suppsoed to be processed.

Am I overlooking something? Why are the jobs not being processed?