Not sure if it’s the same problem but I’ve been having a problem logging in here. The login takes me to a bizarre screen and if I don’t click community on that screen I’m stuck in a loop and not logged in.

Not sure if it's the same problem either, in any case Sonos reached out and let me know that they are aware of the issues with beta site and are working on the solution...

Hi folks. Thanks for reaching out here and appreciate your patience. Just to let you know that we’ve had an issue and appears to be resolved now. Just let us know if you need anything. We and the community are always here to help.

Hi, I have the exact same problem. Error is still appearing on all browsers, all devices.

I've been trying a few times every day but every time I get the http 400 error.

For a short period of time the issue seemed to have been resolved, but  I'm experiencing it again since Saturday

Update for anyone having the same problem. I was able to work around the http 400 error by logging in to the regular sonos site (not beta) and changing the language/country to New Zealand. Then clicking on Beta would redirect correctly into the Beta environment.