There are several things you can do:
- If you are trying to login with your Office 365 account (in xxx@xxxxxxxxxx.onmicrosoft.com format), but having already logged in with your personal account previously, and you will have to log out from your personal account before logging in with your Business account again.
- Please contact your administrator at your office to confirm your login details.
If you are trying to login with an admin account (in admin@xxxxxxxxxx.onmicrosoft.com format), please log out of Office 365 before you login with your new account.