Service Management Portal Customers unable to download attachments (previously they could)

[Patrick Doyle]

We have a team-managed service project and are using the REST API to upload attachments to a ticket using 'rest/api/3/issue/{issue_key}/attachments'.  We add a customer-facing comment to the ticket containing a link to the attachment.  Up until a few months ago, the customer that submitted the ticket was able to download the attachment using the link in the comment, even though he wasn't able to actually see the attachment on the ticket.  This is no longer the case and we are struggling to understand what could have changed.  Has anyone else experienced this or know of a workaround?  Our customers are internal users and they all have Atlassian accounts and have to be logged in in order to view their tickets.