Organizational Account authentication problem

I have encountered a new authentication problem using an organizational account with Get Data > From Web. The data source is Dynamics 365 CE on-premises (https://ce.xxx.com/api.data/v9.1), authenticating through ADFS with MFA. This has been working without any issues until recently. When I attempt to refresh the query, I get an ADFS pop-up window for username and password, as expected. However, the window then closes without the expected MFA prompt. The "Access Web content" window does say "You are currently signed in," but does not query successfully, instead displaying the error "We couldn't authenticate with the credentials provided. Please try again."

The most distinctive symptom, is that clicking the "Sign in as different user" button does not work. It just quickly opens and closes an empty window, instead of the expected ADFS username/password page.

In Power BI Desktop everything works. The connection and query are successful, and the "Sign in as different user" button successfully displays both the initial ADFS username/password window and the subsequent MFA dialog.

Excel version: Microsoft® Excel® for Microsoft 365 MSO (Version 2512 Build 16.0.19530.20226) 64-bit