Problem (Re-)activating Microsoft Office 2021 for Mac in macOS Sequoia

I have a Mac Studio with an external SSD. The SSD has never been attached to anything other than that one Mac Studio. The SSD has a container with four volumes: two boot volumes, a volume for applications not distributed as part of macOS, and a volume with my home directory. I bought a lifetime (i.e., one-time purchase) license for Microsoft Office 2021 and installed it on the volume for applications not distributed as part of macOS. When the boot volumes were Ventura and Sonoma, they both saw Office as activated and I could edit and save Office documents stored in my home directory while booted from either Ventura or Sonoma. I replaced Ventura with Sequoia. I encountered some problems and did a clean install, using Migration Assistant to bring over system settings and related files from Sonoma. I now find that Office is still activated when I boot Sonoma, but is not activated when I boot Sequoia and I can’t activate it in Sequoia. When I go to https://account.microsoft.com/services/, I can log in and it shows that I’ve purchased Office Home & Business 2021 for Mac. When I boot into Sequoia, open Word, click the Activate button on the Word start page, I get a window suggesting that I start a one month free trial of Microsoft 365 (which I don’t want to do) and a link to “Restore previous purchase”. When I click that link, I get a window with the heading “Use this Apple Account with Apple Media Services?”. It shows the Email address associated with my Apple ID (this is not the same Email address I used when purchasing the Microsoft license, but the Email address I used when purchasing the Microsoft license is not associated with any Apple account). I click the “Use This Account” button and I get an error message saying “No subscription found. This Apple ID doesn’t have a paid Microsoft 365 subscription”. I don’t understand this Apple Media Services stuff. I just want to login to Microsoft using the Microsoft account that I used when I purchased the Office 2021 license to activate Office 2021 for the Sequoia boot volume.

Do you have any suggestion about how I can activate Office 2021 or failing that, how I can contact a human being at Microsoft for help?

This is the key piece:

It’s trying to activate it as a subscription to Microsoft 365, not as a perpetual license for Office 2021. Since you don’t have a 365 subscription, this process isn’t going to work. Also, your license would be associated with an Apple ID only if you bought the license (perpetual or subscription) through the Mac App Store. Otherwise, it’s just an email address, no necessary relation to your Apple ID.

What is in the “Use this Apple Account” pop-up besides the email address and the “Use This Account” button? Are there any options to try a different email address, or not use an Apple ID at all? If you can set a different email address, temporarily ignore that the window says “Apple Account” and try using the email associated with your actual license.

If that doesn’t work, try this: boot into Sequoia, launch Word, go to the Word menu and select “About Microsoft Word”. What version does it say it is, what type of license (if any) does it say you have, and what’s the copyright date shown at the bottom? Note these things down, then boot into Sonoma and check the same things. Based on the behavior you’re seeing, I’m expecting at least the license information to be different, but I’m curious as to whether the versions and copyright dates match.