The attachment must be in the file area of the current application. During design time this is always **[YourDesignerPath]/files/applications**. You can always reach these files via API ivy.wf.getApplication().getFileArea();ivy.wf.getApplication().getFileArea(); Its also documented here: http://developer.axonivy.com/doc/latest/DesignerGuideHtml/ivy.processmodeling.html#d5e5929

The attachment must be in the file area of the current application. During design time this is always **[YourDesignerPath]/files/applications**. You can always reach these files via API ivy.wf.getApplication().getFileArea();