Same for me, I've tried a stick via wifi and a hard wired Chromecast.
Its every sports channel, yet again Now TV have something wrong with their sports service, and before any staff say it must be my connection this is my speedtest results:-
I had this back today after raising a complaint.
Thanks for contacting NOW TV and letting us know you were facing buffering issues when watching sports.
We apologies for the inconvenience caused to you. We are currently experiencing issues whereby our customers viewing Sky Sports Football with a NOW TV Boosts Pass are experiencing buffering and poor picture quality.
We have escalated this case to our higher team and they will get back to you via email once the issue is fixed.
But my request for confirmation on how much of my spirts pass will be refunded due to an ununsable service was ignored (again..)
The more people that complain might force them to get there finger out. But clearly they will continue to ignore requests for a refund due to a poor service...