Manager can't reply to ticket, change ticket...

From frontend, manager can't reply to the ticket, change ticket status, change ticket category, change ticket priority. Only the user who have created this ticket can. Have any solution (on joomla 3) ?
When manager try to do this on frontend, it goes back to list of tickets (table).
Any solution ?

Furthermore, I would like to receive an invoice for my purchase (attached to the email godardyvan@gmail.com with which I agreed). Can you send me?

Hi Yvan

That's strange. Could you please submit a support ticket sending me administrator and FTP account of your site so that I can check it directly on your site ?

Tuan