Maybe there is a wrong name in Admin -> Manager Configuration -> Bootstrap Script?
But first I think you could try to change the name directly in the bootstrap script just for testing. They are in /srv/www/htdocs/pub/bootstrap .
But also try to figure out if there is just a routing problem to the SuMa Server. If a ping or telnet [suma-server] 443 doesn't work, everything else will also fail.

Regards, Matthias