Have you been directed here because you tried to add a shortcut to an arbitration case, and ERROR (fix) was returned? The solution is as follows: shortcuts are not added by changing {{Casenav}} on an arbitration page to, e.g., {{Casenav|shortcut=WP:ARBPIA}}, so please undo your edit. Then, follow the instructions below in order to add a shortcut. Once you add the shortcut to this page, the associated case's Casenav instances will automatically detect and display the shortcut (with no edits to the actual case page being required).
Template documentationThis child template contains a list of shortcuts to open or closed arbitration cases. If an arbitration shortcut is created, it should be listed here in the following format:
|Climate change = WP:ARBCC
In this example, Climate change is exactly as in the page Wikipedia:Arbitration/Requests/Case/Climate change and WP:ARBCC is the full pagename of the shortcut WP:ARBCC.
The template will then automatically list the template within the header Template:Casenav, in the format of Template:Shortcut. Cases that date from the period when the Casenav header did not exist are not compatible with this template, and should not be changed from the old format of manually transcluding a Shortcut template on the main case page.
If you mistype the Climate change part of the template entry, the Casenav header on the case pages will not be able to detect that there is a shortcut, so a shortcut will not be displayed. If you mistype the shortcut, then the Casenav header will display a shortcut, but it will be red-linked. Therefore, after adding a shortcut here, please check one of the case pages (link: Template:ACOT) to ensure nothing is broken.