If you can't sign in with your Microsoft account email at office.com/myaccount:
Go to www.office.com/setup and enter the 25-character key that came with Office.
You'll see a portion of the Microsoft account you associated with Office.
Click Sign in with your other Microsoft account, and sign in with the correct Microsoft account.
If these steps don't work, try this troubleshooting article.
Article ID: 4027317 - Last Review: 2017 Iyul 29 - Revision: 1