Maybe it's a selective update. I remember for a long time devART and hotmail would only roll out the update to "selected" emails or users who either agreed to be Beta users, or had registered within a certain time but weren't too old. Example being my main hotmail was grandfathered in to the previous UI for a year before they finally forced a switch on me.
It could also be that you need to delete the app entirely, clear cache and such and then redownload from scratch?