Test your syweb installation by pointing your browser to the URL
http://${VHOST_HOSTNAME}/${VHOST_APPDIR}/configtest.php

If you don't want any user interaction, move index_noui.php to index.php.

syweb expects a <host>/*.rrd style directory structure under
/var/lib/symon/rrds. Customize ${MY_INSTALLDIR}/setup.inc
if this is incorrect for your setup.