so, i know this is an old thread, but just in case anyone pulled their hair out at figuring out why some people have 3 columns and some have 2, i figured out what may be a common cause (at least with windows). in the windows ui settings, if you search "make text size bigger", there is an option to set things to zoom 125% ("make everything bigger") and it is the recommended setting so it may be the default setting (pic below). once that is turned to 100% or setting the zoom feature in the browser to lower, i was able to get all 3 columns to show with no problems. i didnt like the change to the windows ui, so i settled on changing the zoom setting in my browser to 80% and that did the trick, all 3 columns on screen.
before -
setting to change -
-or-
final look -
