Glitch automatically serves projects with Transport Layer Security (TLS). When browsers load a TLS secured page (e.g. URLs beginning with `https`), they treat unsecured pages (e.g. URLS beginning with `http` – notice there's no `s` at the end) as unsafe and refuse to load their content. Wiki knows how to work around this problem when an author is logged-in. But for readers visiting pages of other authors, or for new authors who haven't learned this usability trap, the links to unsecured pages are simply not found instead of being transcluded into the browser tab.
This symptom is not unique to glitch. Any wiki guarded with TLS will exhibit this behavior. As it happens, glitch does also serve the wikis over `http`. Authors can invite readers to visit the unsecured URLs when their content references other unsecured wiki sites.
without TLS 
you can visit Start Playing Wiki where transclusion will work for the Long Chain of Pages
with TLS when visiting Start Playing Wiki transclusion fails for the Long Chain of Pages _(unless you are logged into your own wiki)_
# Jargon
_Transclusion_ wikipedia
_TLS (Transport Layer Security)_ wikipedia
_URL (Uniform Resource Locator)_ wikipedia
Wiki is a hypertext. When you click a link you will go to that page. Here we have arranged the pages like rooms in an adventure game. There are things you can do here but you can just zoom through without doing any of them. Then maybe you will play again and do some things. Play it lots of times. You will get good at it.