Thanks for reaching out to us.
In order to resolve this issue, you need to update the SP Entity ID/Issuer in the Service Provider Metadata tab of the Joomla SAML SP Plugin. Currently, this feature is available in our premium plugins. We will add this feature in the free plugin in our upcoming release. So that I have set up a demo Joomla site for you on our cloud with the Enterprise version of the plugin and provided you with the SuperUser credentials. You can configure the Joomla site with Azure AD and test it out the SSO. If you need help with the setup then we can have a screen share meeting where I can help you to configure with Azure AD. I have sent you the email regarding the demo site URL with the credentials.