Creating an Issue does not allow attachments to be added to the Description and Comment fields. When we create an issue, and we want to add an attachment to either the Description field or the Comment field. The screen capture below shows the Description field which shows the attachment button on the ribbon by the Description field.
This attachment button highlighted in yellow below will disappear once it is clicked on. The same thing happens on the Comment field – the attachment button will disappear after the button is clicked. This means that attachments can not be attached to the issue.

The screen capture below shows the same Description field, but it now does not have the attachment button on the ribbon.

Thanks!