Show Mail preview pane in mac mail- os 10.13.3

I can't get my preview pane back on my macbook pro.

No idea how it disappeared.

which happened after i went to preferences to increase preview content lines.

Settings are identical to IMac which does show preview pane (3 columns)

Ive tried turning off and on default view in preferences, restarted my computer and quit mail several times... to no avail