I had 4 marker groups that I created by clicking on marker groups at the top of the page, then using the create a new marker group on the right side of that page. When I created my 5th marker group, I did so by clicking the Marker Groups icon at the bottom of the page and selected "make visible during initial loading". Since then, none of my marker groups appear on the View World page, but they do in the edit page.
Create marker groups with the link at the top of the edit page, then create marker groups using the icon at the bottom of the edit page.
I found the issue. I had custom code in, that was preventing it from showing. Once removed, the issue resolved itself.