Managing personal Outlook.com account settings, security, and privacy
Hello,
Changing the Microsoft account password invalidated the authorization Alexa was using to access the Outlook calendar. The calendar connection is mainly managed through Alexa, rather than through Outlook. I am surprised Amazon support sent you to Microsoft to get support. That's simply wrong.
In the Alexa app, make sure you are signed in with the Amazon account and Alexa profile that originally linked the calendar, then go to:
More > Settings > Preferences > Calendar
Select the Microsoft/Outlook account, the "unlink account" option is listed right under the email address. Then you can add it back.