I had problems initially when watching on Wifi. It would work on LTE. I deleted the app data, app cache and the app and then turned off that feature in Backup & Reset where it restores app preferences when reinstalling apps. Once I reinstalled, it worked ok on Wifi and LTE.
Also, out of curiousity, when setting up your phone, did you restore settings from your old phone? I restored from my M8 and had this problem along with an issue with Google Play Music.
ETA: I turned Wifi Calling off later as it seems to be causing other issues for me. But my Netflix problem was fixed while it was still turned on.