I am trying to use the Asana Add-in feature within outlook to add an email to an existing Asana task along with the email attachments. I am only able to add the email as a comment but the attachments are not being added. I am able to do this if I want to create a new task but not when I try to add to an existing task.
I found a very similar post to what you are experiencing. I am going to link that post here in hopes that the solution found in that post will help you solve what you are experiencing!