I think it may be a problem for the version upgrade. Can be caused only to this?
This discussion is a little outdated, but I came here looking for a solution. With no answer here and after some time, I found our issue with trying to override a specific action was that our package needed a namespace, namespace="/" to be exact.
Our environment is 18.104.22.168, but this may still be relevant to you.
<package name="dk-sso-plugin-actions-default" namespace="/" extends="community-default">