I already did and tried every possible solution before creating this topic. WP Cron works perfectly fine. There are some other cron jobs that work successfully.
By the way the hook “fep_email_interval_event” and its action “Fep_Email_Beautify->email_interval_event_callback()” looks work too.
But somehow it does not send email until you change those two settings; “Email Sending Interval” and “Emails send per interval”

Best Regards