Netflix on 51.1.0

Sorry if this is old hat to some people, but it's new to me and I couldn't find a way to search the forum by keyword...

FF Portable 51.1.10 won't play Netflix (W7 Pro, W10 Pro) for me, in fact earlier versions used to, but it stopped about a year ago. I read about the FF open code and DRM issue, so I tried FF (also 51.1.0) from Mozilla. It plays Netflix just fine!

Any idea why FF Portable won't? Thanks,

Kevin