The expiration date of the certificate of our VPNsec service was apparently not yet checked regularly. This made it possible for the certificate to expire. We put a new certificate into place within an hour. Of course we will check this certificate regularly from now on. For Apple/Mac we needed to construct a new mobileconfig, this took some time, because in the meantime RU had moved to a different Certificate Authority. For Apple macOS this was ready at the end of Feb. 4, with a new installation procedure. For Apple iOS (iPhone/iPad) the old profile has to be deleted and a new mobileconfig has to be installed.