Missing core UI functionality (Page Title, Tabs, Primary admin actions)

A few weeks ago I noticed that some core functionality (mainly Page Title, Tabs and Primary admin actions) went missing from my UI in Drupal 8.

There were a number of different people working within the system at the time and I can’t say for certain what or what wasn’t changed. Having said that, I have added the core blocks to the ‘content’ area of my block layout and this functionality still will not appear.

Is there something I’m missing? Is there something else I need to be doing in order to get the core blocks to appear?

Drupal version: 

Source: https://www.drupal.org/taxonomy/term/22/feed