Chrome Developer Tools Response/Preview Tab "Pretty Print" or "Formatting"
In your screenshot, you just select the 'preview' tab. Works for me, anyway. Maybe you don't have the Content-Type response header set correctly?
It works if the response code is 200. (Maybe if its 2xx). I found it doesn't work if the response code is 500, though.
An other way to handle this, is to right click the request in the network tab of the developers tools and select "Copy Response". Then in the console window enter the following:
var a = Then paste and hit enter.
Next enter the following:
aThen hit enter again, the entire JSON response will be displayed in an expandable/collapsible form.