I recently updated the OS on my late 2015 iMAC to macOS Sierra. I did this by installing a fresh OS and not upgrading from a previous OS. I installed Plex Media server on my iMac from scratch (also made sure it was up-to-date). I then loaded the NFL Network plugin by downloading from within the servers website by clicking on the Install Channels button and finding from there.
I verified my user name and password by logging into NFL's Gamepass via browser (Chrome) and was able to play an archived game without issue. When I try to access the the same media from within the PLEX media server through the NFL Networks plugin I am unable to view the game. I get an error message "There was a problem playing this item." I can view the NFL.com videos (and specific team video) without issue.
I've included the server log files.
I'd appreciate any help to resolve so this American in Australia can watch his games! :)