New Outlook shows "Copilot isn't available" despite active Microsoft 365 Personal + Copilot license

I have an active Microsoft 365 Personal subscription that includes Copilot. Copilot works fine at copilot.microsoft.com, but in the new Outlook app (Windows 11), clicking the Copilot icon immediately shows:

"Copilot isn't available. You no longer have access to Copilot."

This happens under both connected accounts in Outlook - the Microsoft account itself (which holds the Copilot license) and an added secondary email account. Neither shows Copilot.

Already tried with Microsoft support (5+ hours), no change in the error: toggling Copilot on/off, refreshing the Office 365 license, removing/re-adding the account, repairing the Outlook app, a full Windows 11 in-place upgrade, and testing under a brand-new Windows user profile.

Support suggested a licensing limitation (Copilot sharing needs a work/school account), but that doesn't fit since Copilot doesn't work even under the account that actually holds the license - only on the Copilot website, not in Outlook.

Has anyone seen this exact combination - license confirmed active, Copilot works on the web, but not in the new Outlook app on any account? Looking for a known fix.