Situation: You signed-up with Username & Password but want to transition your user to a Microsoft login for SSO
Is the email you signed-up with your official Microsoft email (not an alias)
If so, click on your Personal Profile from beneath your avatar (top right) then click the Add Microsoft button at the top of the page
We will match the email in our system with the one you authenticate with Microsoft SSO and from now on you will be able to use Microsoft to Log in.
Let us know if this does not work for your special case!