This only applies to Xero
Xero doesn't send the attachment with the email when the email is triggered by an external system like SortScape. When using Xero with Sortscape, invoices are created and managed entirely within the Xero system. Sortscape is responsible for sending the invoice details to Xero, which then takes over the invoicing process. This ensures that users can leverage Xero’s robust invoicing capabilities while Sortscape facilitates the integration by transmitting key details.
Xero are aware of the limitation and have an open feature request where you can vote on fixing this here https://xero.uservoice.com/forums/5528-accounting-api/suggestions/39240961
To address the PDF attachment limitation, you can enable the "Email Xero invoices from SortScape?" setting in your Xero integration settings. When turned on, invoices will be emailed from SortScape with the PDF attachment included, effectively addressing the API restriction. If you ever need to edit the email template, you can do so from the Invoice notifications admin screen.