For the newsletter system to be active you are required to install and activate the plugin named 'Newsletter'.

Please navigate to Admin Dashboard > Plugins > Add new

https://downloads.intercomcdn.com/i/o/514475949/f7a529136b60330420a60c66/image.png

Once you click install here make sure to activate the plugin here:

https://downloads.intercomcdn.com/i/o/514476413/569dd7ddcc150108bc479b02/image.png

Follow this setup wizard tutorial from Newsletter to finish the setup

https://youtu.be/zmVmW84Bw9A