I have the Account Settings > HTML Header > system default selected in Marketing Cloud. In the preview & test you can see ' to view email as webpage go here' appear at the top of the email.
However, once the email is sent (live send) it doesn't appear on the email.
If I add the view email as webpage code to a block in an email, it displays correctly (not twice just the once from where I've manually added it)
Does anyone know anything that needs to be enabled or put in the email to make this work?