Content Type Items Are Not Selectable When Editing a Page

The problem

In Sitefinity, content types with a parent-child structure may not be selectable when editing a page. These content types include Enhanced Cards, FAQ, Newsroom & Articles, and others. When editing the items that you want to show up, the items will not show up if they were previously selected, and when searching for new ones they appear to not exist. This issue is more likely to occur when the items in question haven't been published for several years.

In this screenshot you can see we have an example enhanced card deck with 3 cards that haven't been published in several years.

When trying to edit the cards to change the selection, the current selection is empty even though the page is showing these three cards already.

Even clicking the 'Select' button from the previous screenshot does not show the cards that exist.

The Workaround 

The content type items that you are trying to show, whether it is the parent (an enhanced card deck) or a child (an enhanced card), you must re-publish the item in order for it to show.

First select all of the items that are not selectable. A 'Bulk actions' button will appear at the top. If you only select one item, this will be called 'Actions'. Click that and for multiple items click 'Publish'. For a single item you will need to click 'Unpublish' and then 'Publish'.

After re-publishing the items the last modified date should be 'Today' and there will be a green success message stating how many items were published.

If you had previously selected these items, they should now be visible when editing the widget.

If you click the 'Change' button to see the full list of available cards, those that were previously not shown are available to be added/removed from the selection.