Log into the server as “root” (however you prefer to do that) and ‘su -m asterisk’. Enter the asterisk password (it’s probably blank) and ‘cd’ to /etc
From there, enter ‘fwconsole restart’. It will either tell you that asterisk isn’t running and start it, or stop asterisk are restart it.
I’m going to guess you will get an error message on the “asterisk start” part.
Enter ‘tail /var/log/asterisk/full’ and look at the last 20 lines. Your answer for why Asterisk isn’t starting should be right there.