You don't import projects into Gerrit. You point it to your git repos and it operates directly on them.
I'd look at the log file for gerrit to see if it's complaining about any paths or anything.
One tip: for us, /etc/default/gerritcodereview is sourced by test_site/bin/gerrit.sh. In it, we set the umask to '2' so that files and directories created by gerrit will be group-writable. This is important if you have different users using gerrit, which is
the whole point.