Please try signing in using all your personal email addresses in case you bought Office using a different email address. To restore all features of Office, you'll need to fix the problem that's causing activation to fail.
If Office activation fails, you'll see Unlicensed Product or Non-commercial use / Unlicensed Product in the title bar of your Office apps, and most features of Office are disabled. When clicking 'Additional licence data' I DO get a warning against an alarmingly pink background: 'Activation required'. However, my fiddling must have helped somewhat as next day everything seemed alright again: no error messages when starting any Office application and when clicking 'Account' I see the reassuring text 'Product Activated'. (First it was 'this code is already registered, then 'not a valide product code'.) I tried to activate it, but this proved impossible. After years of use, my MS-Office 2013 suddenly claimed to be not yet activated and threatened to stop working.
