Error Message 0x0 when trying to re-install Office 2019 on Mac Tahoe

Hello,

I have a genuine Office Home & Student 2019 for Mac license, still listed in my Microsoft account under Services & Subscriptions and was added on March 30, 2022. 

Microsoft Support confirmed that my Office Home & Student 2019 license is genuine, valid, and should still be activatable. However, activation fails with error 0x0 immediately after entering my email. And the support argues that they ended their support years ago, that I should rather buy Office 2024.

What makes me think this is not a local Mac issue is that Office stopped activating on my previous Mac (Big Sur) a few months ago, before I replaced it. I recently bought a new Mac and the exact same problem persists.

My configuration:

- MacBook Air M4
- macOS Tahoe
- Office 16.78 (installed using the Microsoft-provided installer)
- Office Home & Student 2019 perpetual license

What I have already tried:

- Reinstalling Office completely
- Installing version 16.78 specifically recommended by Microsoft's support
- Running the official Microsoft License Removal Tool
- Removing Office containers and activation data
- Restarting the Mac
- Signing in with the Microsoft account that owns the license

At this point, I'm wondering whether this may be related to Microsoft's activation services for older perpetual Office 2019 licenses rather than a problem on the Mac itself.

Has anyone else seen error 0x0 during activation of Office 2019 for Mac recently? Any clues?
I wonder if there’s a chance to make pressure also, as Microsoft sells license that are supposed to be perpetual…

Thank you