Did the domain expire or something?
I tried to view Jenkins via ci.isa-afp.org instead, but that just redirects to ci.isabelle.systems. Is there another way to see the build server?
the domain (owned by Lars Hupel, supposed to be transferred) is currently in an unclear status.
the Jenkins no longer exists (there is a Isabelle-based build server now, generally reachable under build.proof.cit.tum.de).
actually, most TUM servers are down currently as the cooling aggregates blew up. We expect a temporary solution to be in effect tomorrow night (but who knows how long that actually takes).