Zoho Desk "Send email reply" function attachment IDs not working

Zoho Desk "Send email reply" function attachment IDs not working

In Zoho Flow I am using the "Send email reply" function to reply to customers with an attached invoice. I use the connection with Desk to update the ticket with the attachment and get the id as a response. I then put this id as I have got it from Desk in the invokeUrl response into the Attachment IDs field of the "Send email reply" function. However the attachment is not attaching. I have checked that the attachment to the ticket is creating correctly and it is. I have also ensured that the attachment is public. I don't understand why the attachment is not working, unless the Attachment ID and the id returned by the invokeUrl call are meant to be different. If so, how do I get the correct value for the Attachment ID?