You have got a saml ticket and you are redirected in the UMC via
https://ucs-sso.schein.me/simplesamlphp/module.php/core/loginuserpass.php[..], but after the login you get this error message:
The issuer ‘None’ is not known to the SAML service provider. This is probably a misconfiguration and might be resolved by restarting the univention-management-console-web-server
/var/log/univention/config-registry-replog for un- or resetting of saml ucr variables. Maybe someone changed the configuration without informing you. Then undo the changes if they are wrong.
ucr set umc/saml/idp-server
ucr unset umc/saml/idp-server univention-run-join-scripts --force --run-scripts 92univention-management-console-web-server.inst