Have you tried clearing the cache and data? If not try clearing them and retry. You can find this under settings, apps, google play movies and TV. If that doesn't work try uninstalling the app updates from the same location.
So just got off of the phone with Google and they believe it is an issue with my router and the DRM they use. I have a netgear Wdr 4500. Just for the heck of it I hooked up the nexus to my phone's hotspot and boom it started downloading my movie right away so it must be a setting in my router. Anyone have any ideas of what I my need to change?
If your blocking access or any ports to youtube or the keyword in your router settings that will block google play movies since they are on youtube! and the app connects to that!
I can do everything else apps etc. The weird thing is if I hook up my GS3 to the same WiFi it can download and play movies and the nexus can download them when hooked up to the GS3 via hotspot. Just my phone WiFi and nexus don't play well for some reason.