Hi,
Something here might help:
Activate Office
https://support.microsoft.com/en-us/office/activate-office-5bd38f38-db92-448b-a982-ad170b1e187e
You might also want to reach out to the experts in the dedicated "Office 2016 activation" forum below:
https://answers.microsoft.com/en-us/msoffice/forum/msoffice_install-mso_win10-mso_2016
Best regards,
Leon