If you can't access a website due to a 400 error, follow these steps.

How do I fix error 400 on my smart TV? If you see error 400 while watching online videos on your smart TV, first try reloading the video, then clear the app cache in your TV's settings.

It's possible that the 400 Bad Request error actually isn't anything wrong on your end but is instead something they need to fix, in which case letting them know about it would be very helpful.