When authenticating the API credentials of the provisioning connector of the Office 365 integration, an error appears:

Could not communicate with Office 365 to validate your credentials, received error: 400 Showing a modal dialog box or form when the application is not running in UserInteractive mode is not a valid operation. Specify the ServiceNotification or DefaultDesktopOnly style to display a notification from a service application.

• Microsoft Office 365
• Provisioning
• API Credentials

• The Microsoft admin account used for authentication is using Microsoft MFA.
• The Microsoft admin account used for authentication is subject to a Conditional Access Policy.
• the Microsoft admin account used for authentication has the "Security Defaults" option enabled. Since October 22nd, 2019, Microsoft has enabled the "Security Defaults" option by default for new tenants, ensuring the "new secure-by-default behavior".

1. The Office 365 Admin Account needs to be validated as active, and it must have Global Admin rights.
2. If a new Admin Account needs to be created, ensure it has Global Admin rights in Office 365. 
3. Ensure the Global Admin Account is exempt from all Conditional Access Policies in Azure. To disable the AAD Admin MFA prompt, follow these steps:
   1. Go to the Microsoft Admin dashboard and select Azure Active Directory.
   2. Go to Properties and select Manage Security Defaults. Disable the security defaults by selecting the No option, then clicking Save.

Related References 

• Office 365 Provisioning: 400 Authentication Error