So I finally fixed access to my Movies Anywhere account. My library finally shows up under Purchases. I've watched a couple of movies without issue. 3rd movie it says I need a subscription, but doesn't say to what. This is my own digital copy so no subscription is necessary. I logged on to the Xfinity Stream app on my phone and the movie plays fine.
Update: tried to watch another movie under purchases and it launched the HBO version because apparently the title is on their channel and it is a free preview timeframes. My guess is this could by why I can't watch the other film. Flex is not smart enough to tell the difference between an owned copy and one you have to have a subscription for.
Given lack of knowledge of CS reps in store and on phone, and no response in the forum, I can't really recommend Flex right now unless you have paid streaming services like Netflix and don't care about anything else. The only plus is the box is rent free (additional boxes cost extra). I had really hoped to have FULL access to my Movies Anywhere library, I don't (just a fraction of movies an no tv series). I hoped to have VUDU offered to access the rest of my digital library that is restricted from Movies Anywhere, it isn't. Other streaming devices seem to offer what I'm looking for so I may be switching.