WD Mycloud App

I have the WD app on my iphone 5 and I get errors when trying to stream or watch a movie I have on the NAS. Only m4v files under 4GB will play (when downloaded to the app) or stream. So all my bluray movies which are bigger will not play. I get an error saying “unable to play”. 

The movies play just fine if I download them via iTunes in the native video app. Any reason why this is??

I actually tried using VLC for iOS and it works just fine. I can stream and/or download and play any size mp4 file. Of course this does me no good for remote access, just local access.