Agent Mode continuously loading

Hi all,

I installed Excel Labs today and have tried to use https://www.microsoft.com/en-us/microsoft-365/blog/2025/09/29/vibe-working-introducing-agent-mode-and-office-agent-in-microsoft-365-copilot/ for Excel in the web. However, no matter which prompt I use, it just loads continuously, even when left for hours.

The example above is taken directly from the Agent Mode blog post.

Has anyone got this working? Or know how to resolve this?

I appreciate it's a Preview feature, so happy to wait if it's a temporary glitch, but thought it'd be worth checking.