I don't know if this is KIX4OTRS or OTRS but when I installed KIX4OTRS it divides the ticket in some tabs like articles, core data, attachments, object link, etc.
I realized there are 2 ways to download an attachment, 1- in the attachment tab and 2- in the article tab near to the print and reply button.
As admin both works.
As agent it shows this error "no permission to use this frontend module!"
Only the admin role can click on that?
Because the agent user has all the permission for that queue, he can see the button but received the error.