Just migrated my old rMBP 2012 to new MBP 2018. With the help of Migration Assistant, everything seems as good as the old one, except that Office365 is not activated. When activating Office, it will always fail, reporting some unknown error 0xD0000FFFE.

It seems that the existing license was not correctly migrated.

After some Googling, solutions like deleting folders under ~/Library/Group Container is ridiculously unacceptable, since it will remove all your Outlook inbox folders!

This post has the official software to remove the existing license. Then re-activate Office365 will succeed happily.