Error: The comment you are trying to reply to already has a reply

This error is returned when you try to resend a reply to an Instagram comment via Direct.
You can only reply to a comment via Direct once.

To continue the conversation with the user in direct messages further, you can click on the author's name in the comments feed and, on the right side of the window that opens, go to the dialog with them, or go to the comment window and, also on the right side of the screen, click on "Messages".