Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Dear Theodoros Chatziioannou,
Thank you for your reply. We see that you said that you cannot alleviate the activation process by logging in to both the work account and the personal account.
You do not need to switch accounts repeatedly. Usually the license information is bound to one of your accounts. You need to confirm whether the bound account is a personal account or a work account?
Then use the same account to log in to the Office program.
At the same time, regarding your question about "how to download old versions of Office software", I need to explain to you:
Office for Mac has a special historical version record support article. To download the historical version, you need to find the corresponding version in the link below and click the download link next to it to download it.
Update history for Office for Mac - Office release notes | Microsoft Learn
For example, to download the historical version 16.42, you can directly click on the blue hyperlink information, and the download progress and information will be displayed after clicking.
You can try to see if this helps you install and activate successfully.
Best regards
Zenobia.Z | Microsoft Community Support Specialist