Recently updated to Ubuntu 17.04 and ensured that all updates have been made with SUSO update in terminal and tried to play some Netflix streams. Every time I try to play I get a "... playback error... Problem with Firefox... Firefox is preventing Netflix from starting playback..." and some recommendations to update Firefox to fix the problem.
The error code Netflix gives is F7701-1003
Any suggestions?
You must be able to play DRM protected content to use Netflix.
As stated on Netflix' help page about the specific error code you gave:
If you experience the error code F7701-1003 on your computer, it typically indicates an issue with your browser's Widevine Content Decryption Module (CDM).
According to Mozilla, Firefox can playback DRM protected content using Widevine since version 47, but you might have to enable it first.
Therefore open the "Preferences" and switch to the "Content" tab or type about:preferences#content in your Firefox address bar. There should be a checkbox labelled "Play DRM content", which needs to be checked.
Note that Firefox will download and install Widevine on demand, which means it can take a while after you vsit Netflix the next time again until it finished and Widevine is ready.