How do I get my ask page to work on tumblr?

When I go to the link for my page's ask box, it gives me this error message: "The URL you requested could not be found." I clicked "Customize" and looked for the Community link, but the only headings at the top that I could pick were INFO, THEME, APPEARANCE, PAGES, and ADVANCED. I've switched themes several times and checked all of the customization headings, but my ask page still won't show up, and neither will the COMMUNITY option on the customize page. Can anyone help?