I have found many entries for this issue, but not quite like mine!
I have set the reading settings to a 'welcome!' static front page I created and the posts page to 'Blog' which is a page I created and also added to my main menu. When I click on 'Blog' I only see the last post that was submitted, not all of them.
Site in maintenance for now (and a collaboration, so can't reveal) but any ideas why only one post shows? If I click on the 'uncategorized' (which they all are) I see all 3 posts. I know I can fix this with categories, but as others less savvy will be using the site, I would rather this worked properly.