I can't seem to make that happen.

You need, I think, 10 points before you're allowed to upvote or downvote anything. The intention is to make it a little harder to make fake accounts and upvote your own posts or downvote your enemies'. (Unfortunately it hasn't made it hard enough to stop the disgruntled user who's downvoting almost everything I -- and a few other people -- post, sometimes multiple times with lots of sockpuppet accounts.)