I think that the problem is due to misunderstanding of how osticket works.
It seems that the template “Support Ticket Opened ” from new ticket autoresponse is only send to the client/customer when it’s the customer which open the ticket from interface xxxxx/index.php and not when it’s the staff which open a ticket from interface xxxx/scp/login.php
I don’t know if this functioning is correct but to bypass this problem I do this following thing.
I enabled the function “New Ticket by Staff” and “New Message” in Settings/Global Setting
In email template I have copied all text (subject and Message Body) from “User/New Ticket Autoresponse” to” New Ticket Notice”
Now, when my staff open a ticket my customer receive the email with the subject “Support Ticket Opened ”
I hope this answer will help you.