You use locally installed Agent for Office 365. After enabling multi-factor authentication(MFA) for your Office 365 organization, global administrator credentials are not accepted by Agent for Office 365.
Either the credentials are incorrect or the specified user is not an administrator in Microsoft Office 365
Currently Cyber Protection console interface doesn't support additional layers of authentication when working with Local Agent for Microsoft Office 365.
This possibility will be added in future versions of the product.
There are two possible workarounds to proceed in this case:
1) Switch to using Cloud-to-Cloud Agent for Office 365: see product documentation for more detail.
When doing this you can use the original local Agent to migrate Cloud backups with Office 365 data to a local storage as described in Acronis Backup: how to export Office 365 archives from Cloud to local storage
2) Utilize app password in Office 365 as described in this MS article: To create app passwords using the Office 365 portal. This will allow you to authenticate the application with a special password without 2FA.
(!) Note that this may compromise security as app passwords work like regular passwords without 2FA.