The desktop clients for Outlook and Skype for Business have trouble supporting Multi-factor authentication (MFA). After enabling MFA for your account, you will need to create an "app password" to allow you to log in to these apps.
This article in the following link walks you through the process.
After creating the password, Office will not show it again. We recommend you store it in a secure password manager. If you do not use a password manager like KeePass, LastPass, or OnePassword, do not save the password in an insecure location (e.g. writing it down, saving it in a plain text file, etc.). If you need to enter the password again, go through this same process to create a new password, and if the old one is not in use anymore, delete it from Office 365 on the same page that you create new ones.