Bing Webmaster Tools will undergo scheduled maintenance between 10am and 1pm ET today. The Microsoft Bing Search toolset posted this notice at the top of the tool when you login today.

Here is a screenshot:

So if you are trying to access the tool at bing.com/webmasters and it is not working and it is around this time, this is why.

This was spotted first by Fili on Mastodon who noticed the spelling mistake with the word maintenance.

Forum discussion at Mastodon.