A custom domain changes the SP Entity ID/Issuer and ACS URL. Your IdP still holds the old values, so it rejects the response. Copy the new SP values into your IdP.
- Open the JSM SSO app and go to SSO Configuration.
- Click Edit for the configured IdP.
- Switch from the IdP Configuration tab to the SP Configuration tab.
- Copy the updated SP Entity ID/Issuer and ACS URL.
- Update these values in your IdP configuration.
- Save and test the SSO connection.