Admin / Editor notifications not being sent

I have several sites that the author / person submitting a revision gets notified but the admin /. editor does not get notified.

The issue is not about emails not being delivered. It is also not about the time stamps, messages going to spam, or anything related to the ability to send emails. The site use Postmark for transactional emails and Fluent SMTP to configure and log sent emails.

The issue is that emails are not being sent (by this plugin) to the admin / editor / reviser. They are only being sent to the submitter of the revision.

I have this issue on multiple sites and have tried it in a test environment too.

Disabling plugins does not help and neither does changing the settings for notifications.