There are no obvious reports from Bing if they are.

Can you access BWT?

I can't. I get redirected to the default Bing Search page... but it could be my ISP.

I can't at the moment, but that's probably my connection.

Tried a different path to BWT and got this:

We're working to restore service as soon as possible.

TRY THIS

Refresh the page -- it might be a momentary issue. If you get this message again, please check back soon.

It's working now. (And I know it was working yesterday, because coincidentally I was there. Normally I visit at most once a year.)

I'm still being redirected.

Huh. I thought maybe I'd got a different link bookmarked, but this time I clicked directly on the link in the OP and was taken there without detours. (My bad for forgetting to sign out earlier.)

Clear cache, different browser, reload etcetera? If they goofed and coded a 301 instead of a 302, your browser may be too smart for its own good.

I've run it through a simulator, the 302 redirects to bing.com. It's got nothing to do with the header fields, it's my account... puzzling.

I've tried 3 different browsers. I can get the https://www.bing.com/toolbox/webmaster/ page with the Sign-In button. The first step is to enter email address, OK that works and takes me to the next page where I enter my password. It's when I click OK there that I'm redirected to the Bing Homepage instead of my dashboard.

Fixed by creating new account. All history & settings propagated.