Assuming that you have linked your server to the Hub, then TKLBAM is a "smart backup that will only backup things that have changed. So if nothing has changed yet, then it's expected that an initial backup will be essentially empty.

I suggest that you delete the /tmp/mybackup directory, add a new file to /var/www and try again. I.e.:

rm -rf /tmp/mybackup
echo "this is a test file - if you can read this we're all good" > /var/www/test.txt
mkdir /tmp/mybackup
tklbam-backup --dump=/tmp/mybackup

Then to double check it works as expected:

cat /tmp/mybackup/var/www/test.txt