You are using a Content Template to display the posts?
I just checked on a local test site and found that if I include the next page tags in a post and display that post without using a Views Content Template (i.e., using just the theme template) then the pagination works.
If I use a Content Template then it does not.
Is that the scenario you are describing?
If so I'll need to pass this on to my colleagues to see if they can identify what needs to be done for it to work.
Well, it doesn't work, so I've passed that information on to my colleagues to see if they can identify a workaround, or if not, propose a change in our templates so that it does work.