Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hi Robert,
Based on my understanding, you are trying to add your mac to the Microsoft Account device list:
Unfortunately, this is not feasible as stated in the following article:
Add a device to your Microsoft account
But, that's not going to affect you activating your Office subscription on your new MacBook pro, just sign in with your Microsoft Account when Office ask you to activate.
If you have different concerns on this, please keep us informed.
Regards,
Alex Chen