Login to Centova Cast, go to Server Software, click on IceCast, and grab the path to IceCast that you've entered there. Login to your server via SSH, paste in that path, and add a "-v" (i.e., /usr/bin/icecast2 -v) and make sure it spits out something like "Icecast 2.3.2".
If that works, run:
su - centovacast -s /bin/bash
cd /home/centovacast/vhosts/USERNAME
/usr/bin/icecast2 -c etc/server.conf
Then see what the output is and paste it here if it's not obvious what the problem is.