I have already went through these steps with a QB tech.  They tried everything on their list of items to check and nothing worked.  I did try the steps you suggested again today and it is still not linking the attached document to the invoice email.  My invoice is linking to Outlook, but the document attached to my invoice is not linking to the email.  I am having to manually attach the document to the email.  This was all working fine last week, just started Monday.  I have a case number already on file.  I was hoping that by today a programming update would have fixed the problem.