If you are using 2FA within outlook, you will need to have your IT team complete the below:
Follow this guide to set up APP Password:
https://docs.microsoft.com/en-us/azure/active-directory/user-help/multi-factor-authentication-end-user-app-passwords
Then, you will need to enter the above details in XPLAN under --> --> Diary Sync --> Login
Username - This is the email address linked to your MS Exchange
Password - This is the password you use to access your above email.