The error happens because another authentication method, other than authentication by password, has been used. For example, using a security key to authenticate a user for login instead of typing a username and password. CAS only supports authentication by password on Azure AD SSO setup.
For more information about the SSO authentication methods supported by Azure AD, refer to this Microsoft article: AuthenticationMethods Class.
CAS supports seamless SAML-based single sign-on (SSO) using your corporate account credentials. Once configured, administrators can use their Azure Active Directory account credentials to perform SSO to the CAS management console. Refer to the following documentation to set up SSO in Azure AD for CAS:
For further assistance, contact Trend Micro Technical Support.