Who calls these endpoints?
Microsoft is retiring the SOAP and POX versions of the Bing Webmaster Tools API on August 31, 2026. The replacement is the JSON over HTTP REST API, which has been the documented path for some time. This is the point at which the old one stops answering.
Almost nobody calls a webmaster-tools API by hand. The traffic comes from software: rank trackers pulling Bing impression data, SEO plugins submitting new URLs, reporting dashboards, and one-off scripts wired up when a site launched. Ownership of those integrations is usually diffuse, which is why an API sunset tends to surface as a chart that stopped updating rather than as an error somebody sees.
What to do about it
Ask the tools, not the API
Send one question to whoever supplies your rank tracking, your SEO plugin, and any custom submission script: are you on the Bing REST API. Vendors that migrated will say so immediately. The ones that go quiet are the ones to follow up on before the end of the month.