What I found out was that the lack of effort in the error message is the issue.    The message sounds like QB is having trouble connecting to the internet.    The issue is that it is having trouble sending an email to a particular recipient.   I have some clients with multiple recipients - e.g. [email address removed] and [email address removed] and [email address removed]   if one of their email addresses changes or is disabled, e.g. jane smith no longer works for acme and her email account has been disabled, instead of getting a useful message e.g. unable to send email to [email address removed] you get qb has a network failure.

It took a while to figure out the source of the issue as I assumed QB would have better diagnostics.