Server actions with type 'Email' use ir_mail_server.send_email:

 """Sends an email directly (no queuing).

So maybe the condition or Timer for your automated action isn't working?

Note:

email_template.send_mail has a parameter force_send:

:param bool force_send: if True, the generated mail.message is
                immediately sent after being created, as if the scheduler
                was executed for this message only.

Regards.