You can send Quotes directly via email using the "Attach File" button. This function uses the documents folder "EmailAttachmentTemp".
Someone might have accidentally deleted the folder, if I do so, I can use this function anymore as it's not possible to attach files/documents to the email. You also can't manually recreate this folder, as the function expects a prefix, which is only part of the managed package.
Use a fallback folder with the following API name: "ADvendioEmailAttachmentTemp" and make it accessible for all users.