In my case the problem was related to the ldap nss authentication. dbus-daemon is running as messagebus user while libnss-ldap.conf is not readable by anyone except root (600) - so dbus-daemon could not authenticate. Changing permissions to 644 fixed the connection problem.
In my case the problem was related to the ldap nss authentication. dbus-daemon is running as messagebus user while libnss-ldap.conf is not readable by anyone except root (600) - so dbus-daemon could not authenticate. Changing permissions to 644 fixed the connection problem.