Changes for office 2021 pro plus bind:
Since Oct.2021, for bind keys, rules changed, only can bind one same computer.
How to active office 2021 pro plus bind:
open www.office.com login in your email address, input key details then instal it is ok.
Where to find office 2021 pro plus in my account after activated:
open www.office.com login in your email address, then click "service & subscription", you will find the one you needed.