You may run into a situation where a user reports that a link in a published Create List on your site is broken - perhaps it returns a 404.
It's likely that you've had this List published on the site for a while, and within that span of time the external site may have deleted or redirected that URL. Or, if this was an internal link, perhaps you've deleted or redirected one of your own posts.
In this situation, Create still displays the original link that you added, so if that URL is no longer valid, it may now be "broken."
To fix this, it will be necessary to go back in to edit your Create List and swap that broken link out for an updated URL.