Navigation portlet does not appear

I'm trying to add the Navigation portlet to my site. I've tried using the "Manage Portlets" menu, but it is not appearing on the page. There is a News portlet at the bottom, but no other portlets appear. What can I do to fix this? I'm currently using the future_imperfect theme.

I would link to my site to illustrate the issue, but the forum does not allow posting links.

To test if it is the theme, you can just change the theme in the control panel.

Most likely it is because

a) That you put the portlet on a default page and not the 'folder', so the others do not inherit it
b) There is nothing to show in the navigation portlet (you put the root folder to 'an empty place' or 'start level' is to high (change it to 0)

I've just discovered that the Navigation Portlet does appear on the page for the News folder. The trouble is that I have a front page that isn't in a folder. The News portlet appears there but the Navigation one does not. Is there any way I can add it?

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