Do you have any other plugins active on the site?
There are several plugins that have settings that will hide the toolbar for either logged in users, or what some plugins call 'untrusted' user levels.
Make sure no plugin is stopping the toolbar from showing.
As AlphaGolf_fr said, there are also themes that disable the toolbar. Some of them allow you to choose, and some don't.
I know, myself, I found where I had stopped the toolbar from showing using a plugin and then I installed this one and couldn't figure out why it wouldn't show. Then I found where I had previously turned it off and changed that setting in the other plugin and it works fine.
And just to be safe, double check to make sure you have allowed the user level you want to see the toolbar, is checked in the WP Toolbar settings.
Hope this helps some as well.