What happens if the customer uses IdP-initiated SSO while it is not supported?

Using IdP-initiated Single Sign-On (SSO) when it is not supported by the system typically results in an error being displayed. This is because the system is designed to handle specific authentication methods, and when a user attempts to access the service using an unsupported method, the expected authentication flow cannot be completed.

The presence of an error message serves to inform the user that their login attempt has failed due to the method used, prompting them to utilize a supported login approach. This ensures users are aware of the situation and can take corrective action instead of experiencing confusion or further issues, such as hanging applications or unexpectedly logged sessions.

In contrast to other scenarios, such as automatic login or application hangs, the system clearly indicates that the user needs to proceed with a compatible authentication mechanism. The error response is a vital part of maintaining a secure and efficient authentication process.