Is your 4.4.0 version an upgrade from a < 4.4 install?
I think what you’re missing is the article content custom field. In 4.4.0+ RT will set these up for you:
For new deploys we also establish some common defaults for Articles: a General class and a Content textarea custom field.
So before just recently, and for upgrades, you’d have to set this up yourself.
The easiest thing to do is navigate to “Admin > Articles > Custom Fields > Create” enter “Content” for the Name and choose “Fill in one text area” for the Type. Click “Create” and then click “Applies To” in the subnav. From there, check the “Apply globally” checkbox and click “Submit”.
When you return to the screen in your screenshot there should be a place to enter content then.