Glitch?

This site is hosted by MoodleCloud. On their free service they impose various restrictions one of which is not allowing guests direct access without going via the login as guest button. There is a workaround but I think this is why people following links from outside the site get told an activity is hidden when it isn't. Entering the original link a second time does seem to take you to the correct page as does following the links from the Course page.

...of course, on other occasions, I might have just set things up incorrectly!

There is also a problem viewing embedded PDFs on iPads and other iOS devices —it shows only the first page of a multi-page document— but I believe this is to do with that version of Safari rather than moodle.