Cannot install addins

Subject: "Error loading add-ins" / "Access denied to catalog" — cannot install any third-party add-ins (Personal Microsoft 365 account)

I'm unable to install any third-party Office add-ins (tested with Claude by Anthropic for Excel/PowerPoint, and confirmed the issue is not add-in-specific — other add-ins fail identically).

Account type: Microsoft 365 Personal

Steps to reproduce:

1. Open Excel or PowerPoint (desktop, Microsoft 365)
2. Insert → Get Add-ins → search for any add-in → Add
3. Error appears: "Error loading add-ins. One or more add-ins failed to load. See your add-ins."
4. Going to My Add-ins → Refresh produces a second error: "Access denied to catalog."

Troubleshooting already tried (no effect):

• Signing out and back into Office
• Clearing Office 365 cache
• Testing on both desktop and web versions of Office

Workaround found: Manually downloading the add-in's XML manifest and using "Manage my add-ins" in the web version of Office partially works, but the desktop version still fails.

Impact: Cannot use any Office Store add-ins on this personal Microsoft 365 account.

Please advise whether this is a known issue with Personal-tier account permissions to the add-in catalog, and what the fix or workaround is.