Problem with Post Page

I have set page ‘Pensees’ to be my post-page. If you click on the ‘Pensees’ tab, you will see an abridged version of each post, however if you click on any one post to view the full post it will redirect you to an error page.

Error message reads: “Oops! That page can’t be found.
It looks like nothing was found at this location. Maybe try one of the links below or a search?”

Not quite sure why I keep receiving this error msg. Assistance would be lovely!

The page I need help with: [log in to see the link]