I was able to remove two emails from the submission notification list, but I am not able to add one now.

I was able to remove two emails from the submission notification list, but I am not able to add one to replace one of the emails I removed due to the free subscription account we are enrolled in. Why can't I simply replace an email, if we were able to have four originally?

I'm afraid that such an option is available only for paid accounts. What happened, most probably, is that you had the email recipients in Notification when the restriction was implemented.

So, unfortunately, the only way is to upgrade.

Let us know if you have any further questions.

Thank you!