The following error is raised when sending an email with attachment using a Quick Action from a Knowledge article.
"Could not find a relationship for attachment reference: FRS_Knowledge#"
The problem is that we are actually sending the email from another object, in this example we are working with “Issue and Resolution”, so it tries to look for the relationship of that object with the attachment and there is no one defined for this particular object, so it seems that it is not able to use the parent’s one.
This is how it can be solved for “Issue and Resolution”, but it will be similar for the FRS_Knowledge extended objects:
1.- Create a new relationship between “FRS_Knowledge.IssueResolution” and “Attachment” as in the screenshot:
2.- In the AdminUI, open “Automation Tools >> Actions”, and in “FRS_Knowledge.IssueResolution” click on “Add/Edit”
3.- Create the "Send Email" Quick Action for that object, using the new relationship created for the attachment: