Unable to authenticate Exchange account

For whatever reason, I am unable to authenticate my Exchange account within Big Sur on my MacBook Pro or my iMac. Exchange requires a 2-step authentication and it seems Big Sur can't provide this (see screenshots).

This Exchange account was/is active in Catalina, Mojave, etc but any attempts to authenticate in Big Sur is a dead-end; this is an issue as I've had to update the Exchange password per IT rules (90 day new password). This is not an issue on my iPhone (iOS 14), for whatever reason, as the authentication box comes up and I can confirm. Likewise, I can use Office365 online and achieve the same thing via our company's SSO method for confirmation. Updates/new events in either area to Outlook calendar don't show on the Mac Calendar (does show on Mac Outlook calendar of course).

Any idea on how to get this to work on Mac/Big Sur?